Gradual oxidation with heat control

ABSTRACT

Described herein are embodiments of systems and methods for oxidizing gases. In some embodiments, a reaction chamber is configured to receive a fuel gas and maintain the gas at a temperature within the reaction chamber that is above an autoignition temperature of the gas. The reaction chamber may also be configured to maintain a reaction temperature within the reaction chamber below a flameout temperature. In some embodiments, heat and product gases from the oxidation process can be used, for example, to drive a turbine, reciprocating engine, and injected back into the reaction chamber.

BACKGROUND

In some industrial processes such as power generation, steam generation,and thermally driven chemical processing, heat can be provided directlyor indirectly by the combustion of high-energy-content (HEC) fuels, suchas propane or natural gas.

Emissions from landfills and other sources of gas containing volatileorganic compounds (VOCs) are considered pollutants. These waste streamsoften contain too little fuel to sustain combustion on their own. Somemethods of disposing of VOC-containing waste streams use thermaloxidizers of the following types: (1) Fired- or supplemental-firedthermal oxidizers, (2) Catalytic thermal oxidizers, (3) Oxidizers withheat recovery, and (4) Regenerative thermal oxidizers (RTOs).

Fired- or supplemental-fired thermal oxidizers can include a burner, aresidence chamber, a mixing chamber, and an exhaust stack. FIG. 1-1Aillustrates a configuration wherein an air-fuel mixture 6 is provided tothe burner 2 to create a continuous flame and the waste stream 7 isintroduced into the flame and continues to oxide as the hot gases passthrough the mixing chamber 3 and residence chamber 4. If the wastestream 7 is within flammability limits, it may be directly combusted inthe burner 2 in place of the air-fuel mixture 6. The mixing chamber 3 isrequired if the waste stream and burner are separately supplied. Theresidence chamber 4 provides enough time to complete the oxidativechemical reactions. The exhaust stack 5 conveys the products ofoxidation to the atmosphere.

Catalytic oxidizers, as shown in FIG. 1-1B, avoid the creation ofthermal NOx by keeping the oxidation reaction temperature low. A wastestream 7 containing VOCs is provided into a catalytic reaction chamber 8having a large internal surface area coated with a catalyst. Catalyticmaterials include noble metals such as platinum, palladium, and iridiumas well as, for certain VOCs, copper oxide, vanadium, and cobalt. Theconcentration of VOCs in the waste stream 7 must be low enough that thereaction temperatures will not exceed the catalyst maximum usetemperature. The waste stream 7 typically has to be heated to a specifictemperature range appropriate for the catalytic reactivity.

The use of a recuperator 9, as shown in FIG. 1-1C, can reduce theoperating costs of fired thermal oxidizers and catalytic oxidizers. Theexhaust from the reaction chamber 1, which may be by way of exampleeither of the systems of FIG. 1-1A or 1-1B, is supplied to ahigh-temperature recuperator 9 to heat either the VOC-laden waste stream7, as shown in FIG. 1-1C, or the separate combustion air-fuel mixture ifsupplied separately, as shown in FIG. 1-1A. Use of a recuperator 9 canreduce or eliminate the need for supplemental fuel to heat the reactantsto their oxidation temperature.

Lastly, RTOs can be used to oxidize VOCs. In an RTO, heat is stored onan intermediate heat sink material, usually a ceramic solid, forrecovery during an alternate cycle. The cycle uses heat from apreviously heated flow to preheat the VOC-laden waste stream to a highertemperature. If the temperature is sufficiently high, oxidation willtake place due to autoignition, as discussed in greater detail later inthe present disclosure. If the temperature is not high enough,supplemental firing from another fuel and air source may be required.The higher-temperature exhaust is then conveyed through a colder heatsink to capture the energy.

There are different approaches to achieve the cycling of the heatexchange material. FIGS. 1-1D illustrates a system using tworegenerative oxidizers. In the depicted configuration, the waste stream7 is introduced into hot regenerative oxidizer #1. The waste stream isheated as it passes through regenerative oxidizer #1, therebyincrementally cooling the heat sink material with the oxidizer #1starting at the inlet. After the waste stream 7 autoignites, the hotexhaust gas exits from the oxidizer #1 and is provided to the inlet ofoxidizer #2, thereby “regenerating” the stored thermal energy in theheat sink material in oxidizer #2. The oxidized waste stream cools as itpasses through oxidizer #2. When oxidizer #2 is sufficiently heated, thesystem is reconfigured such that the flow from the waste stream 7 isprovided to the inlet of oxidizer #2 and the exhaust from oxidizer #2 isprovided to the inlet of oxidizer #1 to regenerate oxidizer #1. Theprocess cycles between the two configurations so that the oxidizer thatwas previously cooled while heating the waste stream 7 is heated, andvisa-versa. Some RTO designs make use of rotating hardware to variablychange the flow streams between cycles or to move the regenerativeoxidizers between cycles. Another approach is to use a singleregenerative oxidizer but to reverse the flow direction for each cycle.One end of the oxidizer will be preheating while the other end iscapturing heat after the oxidative reaction. The reversing of flowdirection is necessary because the end of the oxidizer proximal to theinlet cools to the point where it can no longer heat the incoming wastestream 7 to a temperature that will initiate the reaction.

SUMMARY

In some circumstances, it is advantageous to dispose oflow-energy-content (LEC) fuel, such as the methane that evolves fromsome landfills, while minimizing undesirable components such as carbonmonoxide (CO) and NOx in the exhaust. In other circumstances, it isdesirable to provide heat from a HEC fuel, such as propane, to drive anindustrial process or generate power without creating these sameundesirable components. To accomplish these operations, an air-fuelmixture formed from one or both of LEC and HEC fuels must reach atemperature that is high enough to convert the VOCs and hydrocarbons inthe fuel to carbon dioxide (CO₂) and water (H₂O) while keeping themaximum temperature of the air-fuel mixture below the temperature atwhich thermal NOx will form. Any conventional open-flame combustionprocess is a candidate to be replaced by a process that reduces theformation of NOx compounds through a reduced-temperature oxidationprocess.

There also is a desire to utilize the energy that is otherwise wastedwhen an LEC fuel is simply being disposed of by being oxidized toconvert the VOCs to CO₂ and H₂O. One of the drawbacks of existingpower-generation systems driven by gas turbines is that a HEC fuel isburned to provide the heat that drives the turbine. It would beadvantageous to provide this heat using the essentially “free” LEC fueland avoid or decrease the expense of purchasing fuel.

The processes described above in FIGS. 1-1A through 1-1D have variousdrawbacks. With respect to the thermal oxidizer of FIG. 1-1A, forexample, if supplemental fuel is required to provide the air-fuelmixture 6, the cost of the fuel is additive to the cost of the process.In addition, the reaction temperatures in the burner 2 are high enoughto form thermal NOx, discussed in greater detail later in the presentdisclosure.

Catalysts can have challenges associated with their use. Noble-metalcatalysts are rare and expensive. The process requires that the wastestream be heated to a specific range using any of a variety of means,including heat recovery as described below, but often is additive to thecost of the process. Catalysts can be rendered chemically inactive dueto processes like sintering, fouling, or volatilization. Waste fuels,such as landfill gas, often contain contaminants that can significantlyshorten the life of the catalyst. To control the reaction temperaturesto avoid volatilization, the fuel composition and process variables aremaintained within predefined limits, adding cost to monitor and adjustthese variables.

Recuperators have several disadvantages. The recuperator is anadditional investment cost for a thermal oxidation system. Recuperatorsalso add pressure drop to the system, increasing the power requirementfor the flow conveyance apparatus, i.e. fans, that move the waste stream7 and air-fuel mixtures 6 through the system. If the recuperatorcontains small passages, they can be subject to fouling and corrosionfrom various exhaust gas constituents. If the temperature of the exhaustgas from the reaction chamber is above the maximum service temperaturefor the materials of a recuperator, additional process equipment isrequired to cool to exhaust prior to introducing the exhaust into therecuperator.

Regenerative oxidizers have the drawbacks that the reconfiguration ofthe flow path between cycles requires significant complexity in eitherhigh-temperature valving and piping or in physically moving the hotregenerative oxidizers. The reconfiguration also interrupts the process,requiring some system for accumulating the waste stream 7 during thereconfiguration operation.

The gradual oxidation (GO) process disclosed herein avoids the drawbacksassociated with conventional systems for processing waste streamscontaining VOCs. The GO process, once through the start-up process,operates on LEC fuel and does not require additional HEC fuel to sustainthe oxidation process. The GO process does not require the use of anexpensive catalyst, thereby reducing the required investment andavoiding the operational hazard of poisoning the catalyst. The disclosedGO process transfers the heat produced by the oxidation of the wastestream into the incoming flow, thereby avoiding the problem ofincrementally cooling the media as seen in regenerative oxidizers andeliminating the need for expensive and potentially unreliable valves aswell as the need for an accumulator to handle the incoming waste streamwhile the regenerative system is reconfigured between cycles.

There also are circumstances wherein it is desirable to use a HEC fuelwhile minimizing the formation of undesirable NOx compounds and CO aswell as reducing unburned hydrocarbons in the exhaust. One of thedrawbacks of existing power-generation systems driven by gas turbinesusing a HEC fuel is that the combustion process occurs at a temperatureat which NOx may form and that there may be some level of remaininghydrocarbons as the mixture falls below the lower flammability limitduring the combustion process.

The disclosed systems use a GO process that occurs within an oxidizer(also referred to herein as a gradual oxidizer, a GO chamber, and a GOreaction chamber) in place of a conventional combustion chamber togenerate the heat that drives the system. In certain configurations, theoxidizer contains a material, such as a ceramic, that is structured tobe porous to a gas flow and retains its structure at temperatures above1200° F.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet, the oxidizer configured to maintaingradual oxidation of the fuel within the reaction chamber; and means fordrawing heat from the reaction chamber, such that when an adiabaticreaction temperature within the reaction chamber approaches a flameouttemperature, heat is drawn out of the reaction chamber to reduce anactual temperature within the reaction chamber to a temperature thatdoes not exceed the flameout temperature.

In certain embodiments, the means for drawing heat from the reactionchamber comprises a heat exchanger. In certain embodiments, the meansfor drawing heat from the reaction chamber comprises a fluid. In certainembodiments, the means for drawing heat from the reaction chambercomprises a means for generating steam. In certain embodiments, themeans for drawing heat is configured to draw heat from the reactionchamber when the actual temperature within the reaction chamberincreases to the flameout temperature In certain embodiments, the systemalso includes a means for raising a temperature of the gas, at the inletof the reaction chamber to above the autoignition temperature of thefuel. In certain embodiments, the means comprises a heat exchangerwithin the oxidizer. In certain embodiments the reaction chamber isconfigured to maintain gradual oxidation of the oxidizable fuel withouta catalyst. In certain embodiments, the means is configured to draw heatout of the reaction chamber when the temperature within the reactionchamber exceeds 2300° F. In certain embodiments, the system alsoincludes a turbine that receives gas from the reaction chamber outletand expands the gas. In certain embodiments, the system also includes acompressor that receives and compresses gas, comprising a fuel mixture,prior to introduction of the fuel mixture into the reaction chamber. Incertain embodiments, the oxidizable fuel comprises at least one ofhydrogen, methane, ethane, ethylene, natural gas, propane, propylene,propadiene, n-butane, iso-butane, butylene-1, butadiene, iso-pentane,n-pentane, acetylene, hexane, and carbon monoxide.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet, the oxidizer configured to maintain agradual oxidation process within the reaction chamber; and a heatexchanger configured to draw heat from the reaction chamber when anadiabatic reaction temperature within the reaction chamber approaches aflameout temperature, such that an actual temperature within thereaction chamber is reduced to a level that does not exceed the flameouttemperature.

In certain embodiments, the heat exchanger is configured to draw heatfrom the reaction chamber when the actual temperature of the reactionchamber increases to the flameout temperature. In certain embodiments,the system also includes a turbine that receives gas from the reactionchamber and expands the gas. In certain embodiments, the system alsoincludes a compressor that receives and compresses gas, comprising afuel mixture, prior to introduction of the fuel mixture into thereaction chamber. In certain embodiments, the heat exchanger isconfigured to raise a temperature of the gas, at the inlet of thereaction chamber, to above the autoignition temperature of the fuel. Incertain embodiments, the heat exchanger comprises a fluid introducedinto the reaction chamber. In certain embodiments, the heat exchanger isconfigured to evacuate the fluid from the reaction chamber. In certainembodiments, the heat exchanger comprises a means for generating steam.In certain embodiments, the reaction chamber is configured to maintaingradual oxidation of the oxidizable fuel without a catalyst. In certainembodiments, the heat exchanger is configured to draw heat out of thereaction chamber when the temperature within the reaction chamberexceeds 2300° F. In certain embodiments, the oxidizable fuel comprisesat least one of hydrogen, methane, ethane, ethylene, natural gas,propane, propylene, propadiene, n-butane, iso-butane, butylene-1,butadiene, iso-pentane, n-pentane, acetylene, hexane, and carbonmonoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of receiving a gas comprising an oxidizable fuel intoan oxidizer having a reaction chamber with an inlet and an outlet, thereaction chamber configured to maintain a gradual oxidation process ofthe fuel within the reaction chamber; and drawing heat from the reactionchamber when an adiabatic reaction temperature within the reactionchamber approaches a flameout temperature, such that an actualtemperature within the reaction chamber does not exceed the flameouttemperature.

In certain embodiments, the method includes the step of expanding gasfrom the reaction chamber in a turbine. In certain embodiments, themethod also includes the step of compressing the fuel with a compressorprior to introduction of the fuel mixture into the reaction chamber. Incertain embodiments, the method includes the step of drawing heat fromthe reaction chamber comprises introducing a fluid into the reactionchamber. In certain embodiments, the method includes the step ofevacuating the fluid from the reaction chamber. In certain embodiments,the fluid is evacuated from the reaction chamber in the form of steam.In certain embodiments, the reaction chamber maintains gradual oxidationof the oxidizable fuel without a catalyst. In certain embodiments, heatis drawn out of the reaction chamber when the temperature within thereaction chamber exceeds 2300° F. In certain embodiments, oxidizablefuel comprises at least one of hydrogen, methane, ethane, ethylene,natural gas, propane, propylene, propadiene, n-butane, iso-butane,butylene-1, butadiene, iso-pentane, n-pentane, acetylene, hexane, andcarbon monoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of receiving a gas comprising an oxidizable fuel intoan oxidizer having a reaction chamber with an inlet and an outlet, thereaction chamber configured to maintain a temperature within thereaction chamber to gradually oxidize the fuel within the reactionchamber; and reducing the temperature within the reaction chamber, suchthat an actual temperature within the reaction chamber remains below aflameout temperature.

In certain embodiments, reducing the temperature comprises drawing heatfrom the reaction chamber. In certain embodiments, the method includesthe step of expanding gas from the reaction chamber in a turbine. Incertain embodiments, the method includes the step of compressing thefuel with a compressor prior to introduction of the fuel mixture intothe reaction chamber. In certain embodiments, reducing the temperaturecomprises introducing a fluid into the reaction chamber. In certainembodiments, the method includes the step of evacuating the fluid fromthe reaction chamber. In certain embodiments, the fluid is evacuatedfrom the reaction chamber in the form of steam. In certain embodiments,the reaction chamber maintains gradual oxidation of the oxidizable fuelwithout a catalyst. In certain embodiments, the temperature is reducedsuch that the temperature within the reaction chamber does not exceed2300° F. In certain embodiments, the oxidizable fuel comprises at leastone of hydrogen, methane, ethane, ethylene, natural gas, propane,propylene, propadiene, n-butane, iso-butane, butylene-1, butadiene,iso-pentane, n-pentane, acetylene, hexane, and carbon monoxide.

In certain embodiments, a method for oxidizing a fuel described hereinincludes the steps of determining a temperature within a reactionchamber of an oxidizer, the reaction chamber having an inlet and anoutlet and being configured to maintain gradual oxidation of anoxidizable fuel; and outputting a signal to reduce the temperaturewithin the reaction chamber when the temperature within the reactionchamber approaches a flameout temperature, such that the temperatureremains beneath the flameout temperature.

In certain embodiments, the signal comprises instructions to draw heatfrom the reaction chamber by introducing a liquid into the reactionchamber. In certain embodiments, the signal comprises instructions toevacuate the fluid from the reaction chamber. In certain embodiments,the instructions to evacuate the fluid from the reaction chambercomprise instructions to evacuate the fluid in the form of steam. Incertain embodiments, the signal to draw heat from the reaction chamberis output when the temperature within the reaction chamber exceeds 2300°F. In certain embodiments, the signal to draw heat from the reactionchamber is output when the temperature exceeds a flameout temperature ofat least one of hydrogen, methane, ethane, ethylene, natural gas,propane, propylene, propadiene, n-butane, iso-butane, butylene-1,butadiene, iso-pentane, n-pentane, acetylene, hexane, and carbonmonoxide.

In certain embodiments, a method for oxidizing a fuel described hereinincludes the steps of determining a temperature within a reactionchamber of an oxidizer, the reaction chamber having an inlet and anoutlet and being configured to maintain gradual oxidation of anoxidizable fuel; and outputting a signal to a heat exchanger to drawheat from the reaction chamber when the temperature within the reactionchamber approaches a flameout temperature.

In certain embodiments, the signal comprises instruction to remove heatfrom the reaction chamber. In certain embodiments, the signal comprisesinstruction to reduce the temperature by introducing a fluid into thereaction chamber. In certain embodiments, the signal comprisesinstruction to evacuate the fluid from the reaction chamber. In certainembodiments, the instruction to evacuate the fluid from the reactionchamber comprises evacuating the fluid in the form of steam. In certainembodiments, the method also includes the step of repeatedlycalculating, based on data of the oxidizable fuel, an adiabatic reactiontemperature within the reaction chamber. In certain embodiments, thesignal to reduce the temperature within the reaction chamber is outputwhen the temperature within the reaction chamber exceeds 2300° F. Incertain embodiments, the signal to draw heat from the reaction chamberis output when the temperature approaches a flameout temperature of atleast one of hydrogen, methane, ethane, ethylene, natural gas, propane,propylene, propadiene, n-butane, iso-butane, butylene-1, butadiene,iso-pentane, n-pentane, acetylene, hexane, and carbon monoxide. Incertain embodiments, the signal to draw heat from the reaction chamberis output when the temperature increases to the flameout temperature.

In certain embodiments, a method for oxidizing a fuel described hereinincludes the steps of determining a temperature within a reactionchamber of an oxidizer, the reaction chamber having an inlet and anoutlet and being configured to maintain gradual oxidation of anoxidizable fuel; and determining, with a sensor, when the temperaturewithin the reaction chamber approaches a flameout temperature of thefuel within the reaction chamber.

In certain embodiments, the method includes the step of outputting asignal to reduce the temperature within the reaction chamber when acalculated adiabatic reaction temperature within the reaction chamberexceeds the flameout temperature. In certain embodiments, the calculatedadiabatic reaction temperature is based on the oxidizable fuel and anoxidant within the reaction chamber. In certain embodiments, the signalcomprises instruction to remove heat from the reaction chamber. Incertain embodiments, the signal comprises instruction to reduce thetemperature by introducing a liquid into the reaction chamber. Incertain embodiments, the signal to reduce the temperature within thereaction chamber is output when the temperature within the reactionchamber exceeds 2300° F. In certain embodiments, the signal to draw heatfrom the reaction chamber is output when the temperature exceeds aflameout temperature of at least one of hydrogen, methane, ethane,ethylene, natural gas, propane, propylene, propadiene, n-butane,iso-butane, butylene-1, butadiene, iso-pentane, n-pentane, acetylene,hexane, and carbon monoxide.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet, the oxidizer configured to maintainan oxidation process without a catalyst; a detection module that detectswhen at least one of a reaction temperature within the reaction chamberapproaches a flameout temperature of the fuel within the reactionchamber and a reaction chamber inlet temperature approaches anautoignition threshold; and a correction module that outputsinstructions, based on the detection module, to change at least one ofremoval of heat from the reaction chamber, and the inlet temperature ofthe reaction chamber; wherein the correction module is configured to atleast one of maintain an actual temperature within the reactiontemperature to below the flameout temperature and maintain the inlettemperature above the autoignition threshold of the fuel.

In certain embodiments, the correction module outputs instructions toremove heat from the reaction chamber by a heat exchanger. In certainembodiments, the correction module outputs instructions to remove heatfrom the reaction chamber by a fluid. In certain embodiments, thecorrection module outputs instructions to raise the inlet temperature.In certain embodiments, a heat exchanger positioned within the reactionchamber. In certain embodiments, the reaction chamber is configured tomaintain oxidation of the oxidizable fuel beneath the flameouttemperature. In certain embodiments, the correction module outputsinstructions to remove heat from the reaction chamber when thetemperature within the reaction chamber exceeds 2300° F. In certainembodiments, a turbine that receives gas from the reaction chamber andexpands the gas. In certain embodiments, the system also includes acompressor that receives and compresses gas, comprising a fuel mixture,prior to introduction of the fuel mixture into the reaction chamber. Incertain embodiments, the oxidizable fuel comprises at least one ofhydrogen, methane, ethane, ethylene, natural gas, propane, propylene,propadiene, n-butane, iso-butane, butylene-1, butadiene, iso-pentane,n-pentane, acetylene, hexane, and carbon monoxide.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet, the oxidizer configured to maintainan oxidation process without a catalyst; a detection module that detectswhen at least one of a reaction temperature within the reaction chamberapproaches a flameout temperature of the fuel within the reactionchamber and a reaction chamber inlet temperature approaches anautoignition threshold; and a correction module that outputsinstructions, based on the detection module, to at least one of maintainan actual temperature within the reaction temperature to below theflameout temperature or maintain the inlet temperature above theautoignition threshold of the fuel.

In certain embodiments, the correction module outputs instructions to aheat exchanger to remove heat from the reaction chamber. In certainembodiments, the correction module outputs instructions to remove heatfrom the reaction chamber by a fluid. In certain embodiments, thecorrection module outputs instructions to raise the inlet temperature.In certain embodiments, the system also includes a heat exchangerpositioned within the reaction chamber. In certain embodiments, thereaction chamber is configured to maintain oxidation of the oxidizablefuel beneath the flameout temperature. In certain embodiments, thecorrection module outputs instructions to remove heat from the reactionchamber when the temperature within the reaction chamber exceeds 2300°F.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet, the oxidizer configured to maintainan oxidation process without a catalyst; and a processor that detectswhen at least one of a reaction temperature within the reaction chamberapproaches a flameout temperature of the fuel within the reactionchamber and a reaction chamber inlet temperature drops approaches anautoignition threshold.

In certain embodiments, a correction module that, based on theprocessor, reduces an actual temperature within the reaction chamber toremain beneath the flameout temperature of the fuel by removing heatfrom the reaction chamber. In certain embodiments, a correction modulethat, based on the processor, raises the inlet temperature above theautoignition threshold of the fuel by increasing a residence time of theoxidizable fuel within the reaction chamber.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of receiving a gas comprising an oxidizable fuel intoan oxidizer having a reaction chamber with an inlet and an outlet, thereaction chamber configured to maintain an oxidation process of the gas;and changing at least one of removal of heat from the reaction chamberand an inlet temperature of the reaction chamber when at least one of anactual temperature within the reaction chamber approaches or increasesto a flameout temperature of the fuel and the reaction chamber inlettemperature approaches or drops below an autoignition threshold of thefuel.

In certain embodiments, the actual temperature of the reaction chamberis maintained below the flameout temperature. In certain embodiments,the inlet temperature of the reaction chamber is increased to a levelthat will support oxidation of the fuel without a catalyst. In certainembodiments, the inlet temperature is increased to above theautoignition threshold. In certain embodiments, a temperature of the gasis increased by a heat exchanger located within the reaction chamber. Incertain embodiments, the method also includes the step of expanding gasfrom the reaction chamber outlet in a turbine or a piston engine. Incertain embodiments, the method also includes the step of compressingthe fuel with a compressor prior to introduction of the fuel mixtureinto the reaction chamber. In certain embodiments, removal of heat fromthe reaction chamber comprises introducing a liquid into the reactionchamber. In certain embodiments, the method also includes the step ofevacuating the liquid from the reaction chamber. In certain embodiments,the liquid is evacuated from the reaction chamber in the form of steam.In certain embodiments, the reaction chamber maintains gradual oxidationof the oxidizable fuel without a catalyst. In certain embodiments, heatis removed from the reaction chamber when the temperature within thereaction chamber exceeds 2300° F. In certain embodiments, the oxidizablefuel comprises at least one of hydrogen, methane, ethane, ethylene,natural gas, propane, propylene, propadiene, n-butane, iso-butane,butylene-1, butadiene, iso-pentane, n-pentane, acetylene, hexane, andcarbon monoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of receiving a gas comprising an oxidizable fuel intoan oxidizer having a reaction chamber with an inlet and an outlet, thereaction chamber configured to maintain a gradual oxidation process; andincreasing at least one of removal of heat from the reaction chamberwhen an adiabatic reaction temperature within the reaction chamberapproaches a flameout temperature of the fuel; and an inlet temperatureof the reaction chamber when the reaction chamber inlet temperaturedrops below an autoignition threshold of the fuel.

In certain embodiments, an actual temperature of the reaction chamber ismaintained below the flameout temperature. In certain embodiments, theinlet temperature of the reaction chamber rises to a level that willsupport oxidation of the fuel without a catalyst. In certainembodiments, the inlet temperature rises above the autoignitiontemperature. In certain embodiments, a gas temperature is increased by aheat exchanger located outside the reaction chamber, and the gas ispassed through the heat exchanger prior to being introduced into thereaction chamber.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of receiving a gas comprising an oxidizable fuel intoan oxidizer having a reaction chamber with an inlet and an outlet, thereaction chamber configured to maintain a gradual oxidation processwithout a catalyst; and increasing at least one of removal of heat fromthe reaction chamber when a reaction temperature within the reactionchamber approaches a flameout temperature of the fuel, such that anactual temperature of the reaction chamber is maintained below theflameout temperature; and an inlet temperature of the reaction chamberwhen the reaction chamber inlet temperature drops below an autoignitionthreshold of the fuel, such that the inlet temperature of the reactionchamber is maintained above a level that will support oxidation of thefuel without a catalyst. In certain embodiments, the inlet temperatureis maintained above the autoignition temperature.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet and to maintain an oxidation processwithin the reaction chamber; a detection module that detects when areaction chamber inlet temperature of the gas approaches or drops belowan autoignition threshold of the gas entering the first reactionchamber; and a correction module that outputs instructions, based on thedetection module, to change the inlet temperature of the gas to maintainthe inlet temperature above autoignition threshold, such that the gaswithin the reaction chamber oxidizes without a catalyst.

In certain embodiments, the correction module outputs instructions to aheat exchanger to raise the inlet temperature. In certain embodiments,the heat exchanger is positioned within the reaction chamber. In certainembodiments, the reaction chamber is configured to maintain oxidation ofthe gas beneath a flameout temperature of the fuel within the reactionchamber. In certain embodiments, the system also includes a turbine or apiston engine that receives gas from the reaction chamber and expandsthe gas. In certain embodiments, the system also includes a compressorthat receives and compresses gas, comprising a fuel mixture, prior tointroduction of the fuel mixture into the reaction chamber. In certainembodiments, the oxidizable fuel comprises at least one of hydrogen,methane, ethane, ethylene, natural gas, propane, propylene, propadiene,n-butane, iso-butane, butylene-1, butadiene, iso-pentane, n-pentane,acetylene, hexane, and carbon monoxide.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet and to maintain an oxidation processwithin the reaction chamber; a detection module that detects when areaction chamber inlet temperature of the gas drops toward anautoignition threshold of the fuel; and a correction module that, basedon the detection module, maintains the inlet temperature above theautoignition threshold.

In certain embodiments, the correction module outputs instructions to aheat exchanger to maintain the inlet temperature. In certainembodiments, the heat exchanger is positioned within the reactionchamber. In certain embodiments, the reaction chamber is configured tomaintain an actual temperature within the reaction chamber beneath aflameout temperature of the fuel. In certain embodiments, the systemalso includes a turbine or a piston engine that receives gas from thereaction chamber and expands the gas. In certain embodiments, the systemalso includes a compressor that receives and compresses gas, comprisinga fuel mixture, prior to introduction of the gas into the reactionchamber. In certain embodiments, the oxidizable fuel comprises at leastone of hydrogen, methane, ethane, ethylene, natural gas, propane,propylene, propadiene, n-butane, iso-butane, butylene-1, butadiene,iso-pentane, n-pentane, acetylene, hexane, and carbon monoxide.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet and to maintain an oxidation process;and a heat exchanger that maintains a reaction chamber inlet temperatureabove an autoignition threshold of the fuel, such that the fuel oxidizeswithin the reaction chamber above the autoignition threshold and beneatha flameout temperature of the fuel.

In certain embodiments, a detection module that detects when thereaction chamber inlet temperature approaches the autoignitionthreshold. In certain embodiments, the heat exchanger is positionedwithin the reaction chamber. In certain embodiments, the system alsoincludes a turbine or a piston engine that receives gas from thereaction chamber and expands the gas. In certain embodiments, the systemalso includes a compressor that receives and compresses gas, comprisinga fuel mixture, prior to introduction of the fuel mixture into thereaction chamber. In certain embodiments, the oxidizable fuel comprisesat least one of hydrogen, methane, ethane, ethylene, natural gas,propane, propylene, propadiene, n-butane, iso-butane, butylene-1,butadiene, iso-pentane, n-pentane, acetylene, hexane, and carbonmonoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of determining, in a reaction chamber, with an inletand an outlet, that is configured to maintain an oxidation process of anoxidizable fuel, at least one of an actual reaction temperature of thefuel in the reaction chamber, and an inlet temperature of the reactionchamber; determining, with a sensor, when at least one of the actualreaction temperature approaches or exceeds a flameout temperature of thefuel, and the inlet temperature approaches or drops below anautoignition threshold of the fuel; and determining at least one of areduction of the actual reaction temperature within the reaction chamberto remain below the flameout temperature, and an increase in the inlettemperature to maintain the inlet temperature above the autoignitionthreshold.

In certain embodiments, the reduction of the actual reaction temperaturecomprises removal of heat from the reaction chamber. In certainembodiments, removal of heat from the reaction chamber comprisesintroducing a fluid into the reaction chamber. In certain embodiments,removal of heat further comprises evacuating the fluid from the reactionchamber. In certain embodiments, the reaction chamber is configured toevacuate the fluid in the form of steam. In certain embodiments, theincrease in the inlet temperature comprises directing the fuel through aheat exchanger. In certain embodiments, the heat exchanger is positionedwithin the reaction chamber. In certain embodiments, the flameouttemperature is about 2300° F. In certain embodiments, the oxidizablefuel comprises at least one of hydrogen, methane, ethane, ethylene,natural gas, propane, propylene, propadiene, n-butane, iso-butane,butylene-1, butadiene, iso-pentane, n-pentane, acetylene, hexane, andcarbon monoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of determining, in a reaction chamber, with an inletand an outlet, that is configured to maintain an oxidation process of anoxidizable fuel, at least one of an actual reaction temperature of thefuel in the reaction chamber, and an inlet temperature of the gas at theinlet; determining when at least one of the actual reaction temperatureapproaches or exceeds a flameout temperature of the fuel and a reactionchamber inlet temperature approaches or drops below an autoignitionthreshold of the fuel; and outputting instructions to at least one ofreduce the actual temperature or reduce increase of the actualtemperature within the reaction chamber to be maintained below theflameout temperature, and increase the inlet temperature to be above theautoignition threshold of the fuel.

In certain embodiments, the outputting comprises instructions to removeheat from the reaction chamber. In certain embodiments, the method alsoincludes the step of removing heat from the reaction chamber byintroducing a fluid into the reaction chamber. In certain embodiments,removing heat further comprises evacuating the fluid from the reactionchamber. In certain embodiments, the fluid is evacuated from thereaction chamber in the form of steam. In certain embodiments, theoutputting comprises increasing the inlet temperature by directing thefuel through a heat exchanger. In certain embodiments, the heatexchanger is positioned within the reaction chamber. In certainembodiments, the flameout temperature is about 2300° F. In certainembodiments, the oxidizable fuel comprises at least one of hydrogen,methane, ethane, ethylene, natural gas, propane, propylene, propadiene,n-butane, iso-butane, butylene-1, butadiene, iso-pentane, n-pentane,acetylene, hexane, and carbon monoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of receiving a gas comprising an oxidizable fuel intoan oxidizer having a reaction chamber with an inlet and an outlet, thereaction chamber configured to maintain an oxidation process; and when areaction chamber inlet temperature of the gas approaches or drops belowan autoignition threshold of the fuel, introducing additional heat tothe gas such that the inlet temperature is maintained above theautoignition threshold, and the reaction chamber maintains oxidation ofthe fuel within the reaction chamber without a catalyst.

In certain embodiments, the additional heat is introduced by a heatexchanger. In certain embodiments, the heat exchanger is positionedwithin the reaction chamber. In certain embodiments, the reactionchamber maintains oxidation of the oxidizable fuel beneath a flameouttemperature of the fuel. In certain embodiments, the method alsoincludes the step of a turbine or a piston engine that receives gas fromthe reaction chamber and expands the gas. In certain embodiments, acompressor that receives and compresses gas, comprising a fuel mixture,prior to introduction of the fuel mixture into the reaction chamber. Incertain embodiments, the oxidizable fuel comprises at least one ofhydrogen, methane, ethane, ethylene, natural gas, propane, propylene,propadiene, n-butane, iso-butane, butylene-1, butadiene, iso-pentane,n-pentane, acetylene, hexane, and carbon monoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of receiving a gas comprising an oxidizable fuel intoan oxidizer having a first reaction chamber with an inlet and an outlet,the first reaction chamber being configured to maintain an oxidationprocess of the fuel; and when a reaction chamber inlet temperature ofthe gas approaches or drops below an autoignition threshold of the fuel,increasing the inlet temperature to a level above the autoignitionthreshold.

In certain embodiments, the reaction chamber maintains gradual oxidationof the fuel within the reaction chamber without a catalyst. In certainembodiments, the inlet temperature is increased by a heat exchanger. Incertain embodiments, the heat exchanger is positioned within thereaction chamber. In certain embodiments, the reaction chamber isconfigured to maintain oxidation of the fuel beneath a flameouttemperature of the fuel. In certain embodiments, the method alsoincludes the step of a turbine or a piston engine that receives gas fromthe reaction chamber and expands the gas. In certain embodiments, themethod also includes the step of a compressor that receives andcompresses gas, comprising a fuel mixture, prior to introduction of thefuel mixture into the reaction chamber. In certain embodiments, theoxidizable fuel comprises at least one of hydrogen, methane, ethane,ethylene, natural gas, propane, propylene, propadiene, n-butane,iso-butane, butylene-1, butadiene, iso-pentane, n-pentane, acetylene,hexane, and carbon monoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of in a reaction chamber, with an inlet and anoutlet, that is configured to maintain an oxidation process, determiningwhen an inlet temperature of a gas, comprising an oxidizable fuel, atthe inlet approaches or drops below an autoignition threshold of thefuel; and outputting a signal to increase the inlet temperature of thegas, such that the inlet temperature remains above the autoignitionthreshold.

In certain embodiments, the signal comprises instructions to heat thegas with a heat exchanger. In certain embodiments, the heat exchanger ispositioned within the reaction chamber. In certain embodiments, thereaction chamber is configured to maintain oxidation of the fuel beneatha flameout temperature of the fuel. In certain embodiments, the reactionchamber is configured to maintain oxidation of the fuel below about2300° F. In certain embodiments, the method also includes the step of aturbine or a piston engine that receives gas from the reaction chamberand expands the gas. In certain embodiments, the method also includesthe step of a compressor that receives and compresses gas, comprising afuel mixture, prior to introduction of the fuel mixture into thereaction chamber. In certain embodiments, the oxidizable fuel comprisesat least one of hydrogen, methane, ethane, ethylene, natural gas,propane, propylene, propadiene, n-butane, iso-butane, butylene-1,butadiene, iso-pentane, n-pentane, acetylene, hexane, and carbonmonoxide.

In certain embodiments, a method described herein for oxidizing fuel ina system that receives a gas, comprising an oxidizable fuel, into anoxidizer having a reaction chamber with an inlet and an outlet, thereaction chamber being configured to maintain a gradual oxidation of thefuel without a catalyst, the method comprising detecting when a reactionchamber inlet temperature of the gas approaches or drops below anautoignition threshold of the gas, and outputting instructions toincrease the inlet temperature such that the gas inlet temperature ismaintained above the autoignition temperature, while a temperaturewithin the reaction chamber remains below a flameout temperature.

In certain embodiments, the instructions increase heat transfer to thegas by a heat exchanger. In certain embodiments, the heat exchanger ispositioned within the reaction chamber. In certain embodiments, thereaction chamber is configured to maintain oxidation of the fuel beneatha flameout temperature of the fuel. In certain embodiments, the reactionchamber is configured to maintain oxidation of the fuel beneath about2300° F. In certain embodiments, the method also includes the step of aturbine or a piston engine that receives gas from the reaction chamberand expands the gas. In certain embodiments, the method also includesthe step of a compressor that receives and compresses gas, comprising afuel mixture, prior to introduction of the gas into the reactionchamber.

In certain embodiments, a method for oxidizing fuel described hereinincludes the step of in a reaction chamber, having an inlet and anoutlet, that is configured to maintain an oxidation process,determining, with a sensor, when an inlet temperature of a gas,comprising an oxidizable fuel, at the inlet approaches an autoignitionthreshold of the gas; wherein an actual temperature within the reactionchamber is maintained at a level below the flameout temperature andabove the autoignition threshold, such that gradual oxidation of thefuel is maintained within the reaction chamber.

In certain embodiments, a signal increase the inlet temperature of thegas to remain above the autoignition threshold. In certain embodiments,the signal comprises instructions to increase heat transfer to the gasby a heat exchanger. In certain embodiments, the heat exchanger ispositioned within the reaction chamber.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet, and to maintain an oxidation processof the gas; and heat exchange media disposed within the reactionchamber, the media configured to maintain an internal temperature of thereaction chamber below a flameout temperature and to maintain a reactionchamber inlet temperature of the fuel to be greater than an autoignitiontemperature of the fuel; wherein the media is configured to circulateoutside the reaction chamber and thereby draw heat from the reactionchamber to maintain the internal temperature below the flameouttemperature.

In certain embodiments, circulation of the media is configured to heatgas at the inlet and to maintain the inlet temperature of the fuel abovethe autoignition temperature. In certain embodiments, circulation of themedia is configured to draw heat from the gas within the reactionchamber to maintain the internal temperature of the gas beneath aflameout temperature of the gas. In certain embodiments, the mediacomprises a plurality of steel structures that is circulated through thereaction chamber. In certain embodiments, the media comprises a fluidthat is circulated through the reaction chamber. In certain embodiments,a speed that the media circulates is based on at least one of theinternal temperature and the inlet temperature. In certain embodiments,heat is drawn from the media when the media circulates outside thereaction chamber.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet, the oxidizer configured to maintainan oxidation process of the gas within the reaction chamber; and arecirculation pathway that directs at least a portion of product gas,after oxidation within the reaction chamber, toward the inlet of thereaction chamber and introduces the product gas into the reactionchamber at the inlet; wherein introduction of the product gas increasesan inlet temperature of the gas to be above the autoignition temperatureof the gas.

In certain embodiments, recirculation of the product gas decreases anoxygen content level within the reaction chamber. In certainembodiments, an amount of product gas that is recirculated is based onthe inlet temperature. In certain embodiments, an amount of product gasthat is recirculated is based on an internal temperature of the reactionchamber.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet, the oxidizer configured to maintainan oxidation process of the gas within the reaction chamber; and heatexchange media disposed within the reaction chamber, the mediaconfigured to maintain an internal temperature of the reaction chamberbelow a flameout temperature and to maintain a reaction chamber inlettemperature of the fuel to be greater than an autoignition temperatureof the fuel.

In certain embodiments, the heat exchange media comprises a fluid. Incertain embodiments, the fluid is circulated, and circulation of themedia is configured to heat gas at the inlet and to maintain the inlettemperature of the gas above the autoignition temperature of the gas. Incertain embodiments, the heat exchange media comprises sand. In certainembodiments, the heat exchange media comprises a plurality of uniformlystacked structures. In certain embodiments, the heat exchange mediacomprises a plurality of stacked disk, each having a plurality ofapertures through which the gas is permitted to flow. In certainembodiments, heat exchange media is configured to conduct heat withinthe reaction chamber toward the inlet, whereby gas being receivedthrough the inlet is heated to above the autoignition temperature.

In certain embodiments, a split cycle reciprocating engine describedherein includes an intake that receives an air-fuel mixture, the mixturecomprising a mixture of air and a gas fuel; a compression chamber,coupled to the reciprocating engine that compresses the mixture in areciprocating piston chamber; an oxidation chamber that is configured toreceive the mixture from the compression chamber via a first inlet andto maintain oxidation of the mixture at an internal temperature beneatha flameout temperature of the mixture and sufficient to oxidize themixture without a catalyst; and an expansion chamber, that receivesoxidation product gas from the oxidation chamber and expands the productgas within the expansion chamber via a reciprocating piston.

In certain embodiments, the oxidation chamber is configured to maintainan inlet temperature of the mixture above an autoignition temperature ofthe mixture. In certain embodiments, the system also includes a heatexchanger that is configured to draw heat from the product gas and heatthe mixture prior to introducing the mixture into the oxidation chamber.In certain embodiments, the heat exchanger comprises a tube-in-tube heatexchanger. In certain embodiments, the system also includes a heatexchange media disposed within the oxidation chamber. In certainembodiments, the media is configured to maintain the internaltemperature of the oxidation chamber below a flameout temperature byconducting heat toward the inlet of the oxidation chamber, and whereinmedia at the inlet of the oxidation chamber is cooled by the mixturebeing introduced into the oxidation chamber. In certain embodiments, thefuel comprises at least one of hydrogen, methane, ethane, ethylene,natural gas, propane, propylene, propadiene, n-butane, iso-butane,butylene-1, butadiene, iso-pentane, n-pentane, acetylene, hexane, andcarbon monoxide.

In certain embodiments, a split cycle reciprocating engine describedherein includes a reciprocation cycle comprising at least onecompression chamber having therein a reciprocating piston and at leastone expansion chamber having therein a reciprocating piston; and aheating cycle comprising an intake that receives a gas air-fuel mixturecomprising a mixture of air and a gas fuel, the intake being configuredto direct the mixture to the compression chamber; a reaction chamber,configured to receive the mixture from the compression chamber and tomaintain oxidation of the mixture at an internal reaction chambertemperature sufficient to oxidize the mixture without a catalyst;wherein the expansion chamber is configured to receive oxidation productgas from the reaction chamber and to expand the product gas within theexpansion chamber via the reciprocating piston.

In certain embodiments, the reaction chamber comprises an inlet, and thereaction chamber is configured to maintain an inlet temperature of themixture at the inlet above an autoignition temperature of the mixture.In certain embodiments, the system also includes a heat exchanger thatis configured to draw heat from product gases of the reaction chamberand heat the mixture prior to introducing the mixture into the reactionchamber. In certain embodiments, the heat exchanger comprises atube-in-tube heat exchanger. In certain embodiments, the product gasesare directed back into the reaction chamber and combined with theair-fuel mixture introduced into the reaction chamber. In certainembodiments, the system also includes a heat exchange media disposedwithin the reaction chamber. In certain embodiments, the media isconfigured to maintain the internal temperature of the reaction chamberbelow a flameout temperature of the mixture by conducting heat toward aninlet of the reaction chamber, and wherein media at the inlet of theoxidation chamber is cooled by the mixture being introduced into theoxidation chamber. In certain embodiments, the fuel comprises at leastone of hydrogen, methane, ethane, ethylene, natural gas, propane,propylene, propadiene, n-butane, iso-butane, butylene-1, butadiene,iso-pentane, n-pentane, acetylene, hexane, and carbon monoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of receiving a gas air-fuel mixture through anintake, the mixture comprising a mixture of air and a gas fuel;compressing the mixture with a compression chamber, the compressionchamber being coupled to a reciprocating engine and compressing themixture in a reciprocating piston chamber; oxidizing the mixture in areaction chamber that is configured to receive the mixture from thecompression chamber via an inlet and to maintain oxidation of the fuelat an internal temperature of the reaction chamber without a catalyst;and expanding heated product gas from the reaction chamber in areciprocating piston chamber coupled to the reciprocating pistonchamber, thereby driving the reciprocating engine.

In certain embodiments, the internal temperature of the reaction chamberis maintained beneath a flameout temperature of the fuel. In certainembodiments, the steps also include removing heat from the reactionchamber when a temperature in the reaction chamber approaches or raisesabove the flameout temperature. In certain embodiments, a temperature ofthe mixture at the inlet is maintained above an autoignition temperatureof the mixture. In certain embodiments, the steps also include heatingthe mixture by a heat exchanger prior to oxidizing the mixture in thereaction chamber. In certain embodiments, the heat exchanger is locatedwithin the reaction chamber. In certain embodiments, an inlettemperature of the mixture at the inlet of the reaction chamber isbeneath an autoignition temperature of the mixture. In certainembodiments, the mixture is heated within the heat exchanger to atemperature above the autoignition temperature.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of compressing an air-fuel mixture, comprising amixture of air and a gas fuel, in a reciprocating piston compressionchamber coupled to a reciprocating engine; oxidizing the mixture in areaction chamber, configured to receive the mixture from the compressionchamber via a inlet, above an autoignition temperature of the fuel andbeneath a flameout temperature of the fuel; and expanding product gasfrom the reaction chamber in a reciprocating piston chamber coupled tothe reciprocating engine, thereby driving the reciprocating engine.

In certain embodiments, an internal temperature of the reaction chamberis maintained beneath a flameout temperature of the mixture. In certainembodiments, the method also includes the step of removing heat from thereaction chamber when an adiabatic temperature in the reaction chamberapproaches or raises above the flameout temperature. In certainembodiments, a temperature of the mixture at the inlet is maintainedabove an autoignition temperature of the mixture. In certainembodiments, the method also includes the step of heating the mixture bya heat exchanger prior to oxidizing the fuel in the reaction chamber. Incertain embodiments, the heat exchanger is located within the reactionchamber. In certain embodiments, an inlet temperature of the mixture atthe inlet of the reaction chamber is beneath an autoignition temperatureof the mixture. In certain embodiments, the mixture is heated within theheat exchanger to a temperature above the autoignition temperature.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of directing an air-fuel mixture, comprising amixture of air and a gas fuel, to be compressed in a reciprocatingcompression piston coupled to a reciprocating engine; directing themixture from the compression piston to a reaction chamber, configured togradually oxidize the mixture within the reaction chamber above anautoignition temperature of the mixture and beneath a flameouttemperature of the mixture; and directing product gas from the reactionchamber to be expanded in a reciprocating expansion piston coupled tothe reciprocating engine, thereby driving the reciprocating engine.

In certain embodiments, the method also includes the step ofdetermining, with a sensor, when a temperature in the reaction chamberapproaches or exceeds the flameout temperature. In certain embodiments,the method also includes the step of directing removal of heat from thereaction chamber when the temperature in the reaction chamber approachesthe flameout temperature, such that the temperature in the reactionchamber is maintained below the flameout temperature. In certainembodiments, the method also includes the step of maintaining aninternal temperature within the reaction chamber below about 2300° F.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of determining an oxygen content level within thereaction chamber having an inlet and an outlet and configured togradually oxidize a fuel, in a gas mixture, without a catalyst;outputting instructions to introduce flue gas, received from the outletof the reaction chamber and containing product gases from oxidation ofthe fuel within the reaction chamber, into the reaction chamber based onthe determined oxygen content level.

In certain embodiments, introducing the flue gas comprises mixing theflue gas with the gas mixture. In certain embodiments, the method alsoincludes the step of determining if an internal temperature within thereaction chamber approaches a flameout temperature of the fuel. Incertain embodiments, the method also includes the step of outputtinginstructions to reduce the internal temperature within the reactionchamber when an adiabatic temperature within the reaction chamberapproaches the flameout temperature of the fuel. In certain embodiments,the instructions comprise removing heat from the reaction chamber. Incertain embodiments, outputting instructions is configured to change aflameout temperature of the fuel within the reaction chamber. In certainembodiments, the method also includes the step of determining an inlettemperature of the gas mixture at the reaction chamber inlet. In certainembodiments, the method also includes the step of increasing atemperature of the gas mixture at the inlet when the inlet temperatureapproaches an autoignition temperature of the fuel, such that the inlettemperature is maintained above the autoignition temperature. In certainembodiments, increasing the temperature comprises mixing the flue gaswith the gas mixture at or near the reaction chamber inlet.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of determining at least one of an oxygen contentlevel within the reaction chamber having an inlet and an outlet andconfigured to gradually oxidize a fuel, in a gas mixture, without acatalyst and an inlet temperature of the gas mixture at the reactionchamber inlet; based on at least one of the determined oxygen contentlevel and the inlet temperature, introducing flue gas, received from theoutlet of the reaction chamber and containing heated product gases fromoxidation of the fuel within the reaction chamber, into the reactionchamber when at least one of the determined oxygen content level isapproaching or beyond a predetermined threshold and the inlettemperature is approaching or below an autoignition temperature of thefuel.

In certain embodiments, introducing the flue gas comprises mixing theflue gas with the gas mixture. In certain embodiments, the method alsoincludes the step of determining if an internal temperature within thereaction chamber approaches a flameout temperature of the fuel. Incertain embodiments, the method also includes the step of reducing theinternal temperature within the reaction chamber when an adiabatictemperature within the reaction chamber approaches the flameouttemperature of the fuel. In certain embodiments, reducing the internaltemperature comprises removing heat from the reaction chamber. Incertain embodiments, the method also includes the step of comprisingincreasing the flameout temperature within the reaction chamber byreducing the oxygen content within the reaction chamber.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of determining, with a processor, an oxygen contentlevel within the reaction chamber having an inlet and an outlet andconfigured to gradually oxidize a fuel, in a gas mixture, without acatalyst; and based on the determined oxygen content level, introducingflue gas, received from the outlet of the reaction chamber andcontaining heated product gases from oxidation of the fuel within thereaction chamber, into the reaction chamber.

In certain embodiments, introducing the flue gas comprises mixing theflue gas with the gas mixture. In certain embodiments, the flue gas ismixed with the gas mixture at or near the reaction chamber inlet. Incertain embodiments, the method also includes the step of determining ifan internal temperature within the reaction chamber approaches orexceeds a flameout temperature of the fuel. In certain embodiments, themethod also includes the step of reducing the internal temperaturewithin the reaction chamber when an adiabatic temperature within thereaction chamber approaches or exceeds the flameout temperature of thefuel. In certain embodiments, reducing the internal temperaturecomprises removing heat from the reaction chamber. In certainembodiments, the method also includes the step of changing the flameouttemperature within the reaction chamber by changing the oxygen contentwithin the reaction chamber.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of in a first reaction chamber, with an inlet and anoutlet, that is configured to maintain a gradual oxidation processwithout a catalyst, determining when an inlet temperature of a gasmixture, comprising an oxidizable fuel, at the reaction chamber inletapproaches or drops below an autoignition temperature of the fuel; andwhen the inlet temperature is determined to approach or drop below theautoignition temperature of the fuel, increasing the inlet temperatureof the gas mixture by introducing flue gas, comprising at leastpartially oxidized product gas from the reaction chamber, into the gasmixture at or near the inlet.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of gradually oxidizing a first fuel, in a first gasmixture, in a first reaction chamber that is configured to maintaingradual oxidation of the first fuel within the first reaction chamberwithout a catalyst; introducing flue gas, comprising heated product gasfrom oxidation of the first fuel in the first reaction chamber, into asecond reaction chamber; introducing a second fuel into the secondreaction chamber; and oxidizing the second fuel in the second reactionchamber in a gradual oxidation process without a catalyst; wherein afirst internal temperature within the first reaction chamber ismaintained beneath a flameout temperature of the first fuel.

In certain embodiments, the method includes the step of maintaining asecond internal temperature within the second reaction chamber beneath aflameout temperature of the second fuel. In certain embodiments, themethod also includes the step of reducing the second internaltemperature within the second reaction chamber when an adiabatictemperature within the second reaction chamber approaches or exceeds theflameout temperature of the second fuel within the second reactionchamber. In certain embodiments, reducing the second internaltemperature comprises removing heat from the second reaction chamber. Incertain embodiments, the flameout temperature of the second fuel ishigher than the flameout temperature of the first fuel. In certainembodiments, the method also includes the step of reducing the firstinternal temperature within the first reaction chamber when an adiabatictemperature within the first reaction chamber approaches or exceeds theflameout temperature of the first fuel within the first reactionchamber. In certain embodiments, reducing the first internal temperaturecomprises removing heat from the first reaction chamber. In certainembodiments, the method also includes the step of determining a firstinlet temperature of the gas mixture at the first reaction chamberinlet. In certain embodiments, the method also includes the step ofincreasing the first inlet temperature when the first inlet temperatureapproaches or drops below an autoignition temperature of the first fuelwithin the first reaction chamber, such that the first inlet temperatureis maintained above the autoignition temperature. In certainembodiments, the method also includes the step of determining a secondinlet temperature at a second reaction chamber inlet. In certainembodiments, the method also includes the step of increasing the secondinlet temperature when the second inlet temperature approaches or dropsbelow an autoignition temperature of the second fuel within the secondreaction chamber, such that the second inlet temperature is maintainedabove the autoignition temperature. In certain embodiments, the methodalso includes the step of increasing the second inlet temperaturecomprises introducing the flue gas to mix with the second fuel at ornear the second reaction chamber inlet.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of gradually oxidizing a first fuel, in a first gasmixture, in a first reaction chamber that is configured to maintaingradual oxidation of the first fuel within the first reaction chamberwithout a catalyst; introducing flue gas, comprising heated product gasfrom oxidation of the first fuel in the first reaction chamber, into asecond reaction chamber configured to maintain gradual oxidation withouta catalyst; determining, with a processor, an oxygen content levelwithin the second reaction chamber; introducing a second fuel into thesecond reaction chamber; and oxidizing the second fuel in the secondreaction chamber in a gradual oxidation process without a catalyst.

In certain embodiments, an amount and distribution within the secondchamber of the introduction of flue gas into the second chamber is basedon the determined oxygen content level. In certain embodiments, a firstinternal temperature within the first reaction chamber is maintainedbeneath a flameout temperature of the first fuel. In certainembodiments, the method also includes the step of maintaining a secondinternal temperature within the second reaction chamber beneath aflameout temperature of the second fuel. In certain embodiments, themethod also includes the step of reducing the second internaltemperature within the second reaction chamber when an adiabatictemperature within the second reaction chamber approaches or exceeds theflameout temperature of the second fuel within the second reactionchamber. In certain embodiments, reducing the second internaltemperature comprises removing heat from the second reaction chamber. Incertain embodiments, the method also includes the step of reducing thefirst internal temperature within the first reaction chamber when anadiabatic temperature within the first reaction chamber approaches orexceeds the flameout temperature of the first fuel within the firstreaction chamber. In certain embodiments, reducing the first internaltemperature comprises removing heat from the first reaction chamber. Incertain embodiments, the method also includes the step of determining afirst inlet temperature of the gas mixture at the first reaction chamberinlet. In certain embodiments, the method also includes the step ofincreasing the first inlet temperature when the first inlet temperatureapproaches or drops below an autoignition temperature of the first fuelwithin the first reaction chamber, such that the first inlet temperatureis maintained above the autoignition temperature. In certainembodiments, the method also includes the step of determining a secondinlet temperature at a second reaction chamber inlet. In certainembodiments, the method also includes the step of increasing the secondinlet temperature when the second inlet temperature approaches or dropsbelow an autoignition temperature of the second fuel within the secondreaction chamber, such that the second inlet temperature is maintainedabove the autoignition temperature. In certain embodiments, increasingthe second inlet temperature comprises introducing the flue gas to mixwith the second fuel at or near the second reaction chamber inlet.

In certain embodiments, a system for oxidizing fuel described hereinincludes a first reaction chamber with a first inlet and a first outlet,the first reaction chamber configured to receive a first gas comprisinga first oxidizable fuel, the first reaction chamber configured tomaintain a gradual oxidation process of the first fuel; and a secondreaction chamber with a second inlet and a second outlet, the secondreaction chamber configured to receive a second gas comprising a secondoxidizable fuel, the second reaction chamber configured to maintain agradual oxidation process of the second fuel; wherein the first andsecond reaction chambers are configured to maintain an internaltemperature in the respective reaction chambers below a flameouttemperature of the respective fuel; wherein the second reaction chamberis configured to receive flue gas comprising heated product gas fromoxidation of the first fuel in the first reaction chamber, into a secondreaction chamber through the second inlet.

In certain embodiments, the system includes a heat exchange mediadisposed within at least one of the reaction chambers, the mediaconfigured to maintain an internal temperature of the reaction chamberbelow an adiabatic flameout temperature. In certain embodiments, atleast one of the first and second reaction chambers is configured toreduce the respective internal temperature when an adiabatic temperaturewithin the respective reaction chamber approaches or exceeds theflameout temperature of the respective fuel. In certain embodiments, atleast one of first and second reaction chambers is configured to reducethe respective internal temperature by removing heat from the respectivereaction chamber by a heat exchanger. In certain embodiments, the heatexchanger comprises a fluid introduced into the respective reactionchamber. In certain embodiments, the heat exchanger is configured toevacuate the fluid from the respective reaction chamber. In certainembodiments, the heat exchanger comprises a means for generating steam.

In certain embodiments, the heat exchanger is configured to draw heatout of the respective reaction chamber when the temperature within therespective reaction chamber exceeds 2300° F. In certain embodiments, thefirst reaction chamber is configured to increase a temperature of thefirst gas at the first inlet when a first inlet temperature, at thefirst inlet, approaches or drops below an autoignition temperature ofthe first fuel. In certain embodiments, the second reaction chamber isconfigured to increase a temperature of the second gas at the secondinlet when a second inlet temperature, at the second inlet, approachesor drops below an autoignition temperature of the second fuel.

In certain embodiments, the second reaction chamber is configured to mixthe flue gas with the second gas when a second inlet temperature of thesecond gas at the second inlet approaches or drops below an autoignitiontemperature of the second fuel. In certain embodiments, distribution ofthe flue gas within the second reaction chamber is based on at least oneof a second inlet temperature of the second gas at the second inlet andthe internal temperature of the second reaction chamber. In certainembodiments, the system also includes a turbine or a piston engine thatreceives gas from at least one of the reaction chambers. In certainembodiments, the turbine receives gas from the second reaction chamber.In certain embodiments, a compressor that receives and compresses gas,comprising a fuel mixture, prior to introduction of the fuel mixtureinto at least one of the reaction chambers. In certain embodiments, thecompressor is configured to compress the second gas prior to introducingthe second gas into the second reaction chamber.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber configured to receive andoxidize a gas mixture comprising an oxidizable fuel in a gradualoxidation process within the reaction chamber; an inlet configured tointroduce fluid into the reaction chamber during the oxidation process,the fluid being at an inlet temperature lower than an internaltemperature of the reaction chamber, such that the fluid is heated as itis introduced into the reaction chamber; and an outlet configured toextract the heated fluid from the reaction chamber; wherein the reactionchamber is configured to maintain the internal temperature above anautoignition temperature of the fuel and below a flameout temperature ofthe fuel.

In certain embodiments, the inlet is configured to introduce a liquidinto the reaction chamber. In certain embodiments, the liquid isintroduced into the reaction chamber by passing through one or morecoils within the reaction chamber. In certain embodiments, the coils arenot in fluid communication with the reaction chamber. In certainembodiments, the liquid is introduced into the reaction chamber byinjecting the liquid into the reaction chamber, such that the liquidmixes with the gas mixture within the reaction chamber. In certainembodiments, the inlet is configured to introduce the fluid into thereaction chamber as a gas. In certain embodiments, the gas is introducedinto the reaction chamber by passing through one or more coils withinthe reaction chamber. In certain embodiments, the coils do not permitmixing of the gas and the gas mixture within the reaction chamber. Incertain embodiments, the gas is introduced into the reaction chamber byinjecting the gas into the reaction chamber, such that the gas mixeswith the gas mixture within the reaction chamber. In certainembodiments, the outlet is configured to extract the heated fluid fromthe reaction chamber as a gas. In certain embodiments, the outlet isconfigured to redirect the gas into the reaction chamber, such that thegas mixes with the gas mixture within the reaction chamber. In certainembodiments, an adiabatic reaction temperature within the reactionchamber approaches a flameout temperature, the fluid is introduced intothe reaction chamber. In certain embodiments, the inlet temperature isbelow an autoignition temperature of the fuel. In certain embodiments,the oxidizable fuel comprises at least one of hydrogen, methane, ethane,ethylene, natural gas, propane, propylene, propadiene, n-butane,iso-butane, butylene-1, butadiene, iso-pentane, n-pentane, acetylene,hexane, and carbon monoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of directing a gas mixture, comprising an oxidizablefuel, to an oxidizer having a reaction chamber configured to receive andoxidize the fuel in a gradual oxidation process within the reactionchamber, the reaction chamber being configured to maintain an internaltemperature above an autoignition temperature of the fuel and below aflameout temperature of the fuel; and introducing fluid into thereaction chamber during the oxidation process, the fluid being at aninlet temperature lower than the internal temperature of the reactionchamber, such that the fluid is heated as it is introduced into thereaction chamber; and extracting the heated fluid from the reactionchamber.

In certain embodiments, the fluid is introduced into the reactionchamber as a liquid. In certain embodiments, the liquid is introducedinto the reaction chamber by passing through one or more coils withinthe reaction chamber. In certain embodiments, the liquid is injectedinto the reaction chamber, such that the liquid mixes with the gasmixture within the reaction chamber. In certain embodiments, the fluidis introduced into the reaction chamber as a gas. In certainembodiments, the gas is introduced into the reaction chamber by passingthe gas through one or more coils within the reaction chamber. Incertain embodiments, the gas is injecting the gas into the reactionchamber, such that the gas mixes with the gas mixture within thereaction chamber. In certain embodiments, the heated fluid is extractedfrom the reaction chamber as a heated gas. In certain embodiments, themethod also includes the step of redirecting the heated gas into thereaction chamber, such that the heated gas mixes with the gas mixturewithin the reaction chamber. In certain embodiments, the oxidizable fuelcomprises at least one of hydrogen, methane, ethane, ethylene, naturalgas, propane, propylene, propadiene, n-butane, iso-butane, butylene-1,butadiene, iso-pentane, n-pentane, acetylene, hexane, and carbonmonoxide.

In certain embodiments, an oxidizer for oxidizing fuel described hereinincludes a reaction chamber having one or more inlets that areconfigured to direct at least one gas of fuels, oxidants, or diluents,into the reaction chamber and one or more outlets that are configured todirect reaction products from the reaction chamber, and a heater that isconfigured to maintain a temperature of one or more of the at least onegas, at or before the one or more inlets, to above an autoignitiontemperature of a resulting mixture within the reaction chamber thatcomprises the at least one gas of fuels, oxidants, or diluents, andwherein the reaction chamber is configured to oxidize the mixture andmaintain an adiabatic temperature and a maximum reaction temperature inthe reaction chamber below a flameout temperature of the mixture.

In certain embodiments, the reaction chamber comprises a single inlet.In certain embodiments, the oxidizer is configured to change a flow ratethat the mixture is introduced into the reaction chamber through theinlet. In certain embodiments, the heater comprises a heat exchangerthat transfers heat from the reaction products to the mixture at orbefore the one or more inlets. In certain embodiments, the heater isconfigured to mix at least one of oxidants or diluents with fuel at orbefore the one or more inlets. In certain embodiments, the oxidizer isconfigured to use heat from the reaction products to generate steam. Incertain embodiments, the oxidizer is configured to use heat from thereaction products to drive a generator for power generation. In certainembodiments, the oxidizer is configured to drive a generator by aturbine or a piston engine that is configured to expand the reactionproducts from the reaction chamber. In certain embodiments, the oxidizeris configured to use heat from the reaction products to heat materialthat is not passed through the oxidizer. In certain embodiments, theoxidizer is configured to change a flow rate that one or more of the atleast one gas of fuels, oxidants, or diluents is introduced into thereaction chamber through the one or more inlets. In certain embodiments,the oxidizer is configured to change a flow rate that the reactionproducts are directed from the reaction chamber through the outlets. Incertain embodiments, the oxidizer also includes a regulator that isconfigured to change at least one of a flow of the mixture or a pressureof the mixture at or near the inlet.

In certain embodiments, an oxidizer for oxidizing fuel described hereinincludes a reaction chamber having an inlet that is configured to directat least one gas of fuels, oxidants, or diluents, into the reactionchamber and an outlet that is configured to direct reaction productsfrom the reaction chamber, and means for maintaining a temperature ofthe incoming gas, at or before the inlet, to above an autoignitiontemperature of a resulting mixture within the reaction chamber thatcomprises the at least one gas of fuels, oxidants, or diluents, whereinthe reaction chamber is configured to oxidize the mixture and maintainan adiabatic temperature and a maximum reaction temperature in thereaction chamber below a flameout temperature of the mixture.

In certain embodiments, the reaction chamber comprises a plurality ofinlets. In certain embodiments, the reaction chamber comprises aplurality of outlets. In certain embodiments, the means for raising atemperature comprises a heat exchanger that transfers heat from thereaction products to the mixture at or before the inlet. In certainembodiments, the means for raising a temperature is configured to mixdiluents with fuel at or before the inlet. In certain embodiments, theoxidizer is configured to use heat from the reaction products togenerate steam. In certain embodiments, the oxidizer is configured touse heat from the reaction products to drive a generator for powergeneration. In certain embodiments, the oxidizer is configured to drivea generator by a turbine or a piston engine that is configured to expandthe reaction products from the reaction chamber. In certain embodiments,the oxidizer is configured to use heat from the reaction products toheat material that is not passed through the oxidizer. In certainembodiments, the oxidizer is configured to change a flow rate that themixture is introduced into the reaction chamber through the inlet. Incertain embodiments, the oxidizer is configured to change a flow ratethat the reaction products are directed from the reaction chamberthrough the outlet. In certain embodiments, the oxidizer also includes aregulator that is configured to change at least one of a flow of themixture or a pressure of the mixture at or near the inlet. In certainembodiments, the oxidizer is configured to change a flow rate that oneor more of the at least one gas of fuel, oxidants, or diluents isintroduced into the reaction chamber through one or more inlets.

In certain embodiments an oxidizer for oxidizing fuel described hereininclude a reaction chamber having one or more inlets that are configuredto direct at least one gas of fuels, oxidants, or diluents, into thereaction chamber and one or more outlets that are configured to directreaction products from the reaction chamber; and a heater that isconfigured to maintain a temperature of one or more of the at least onegas, at or before the one or more inlets, to above an autoignitiontemperature of a resulting mixture within the reaction chamber thatcomprises the at least one gas of fuel, oxidants, or diluents, whereinthe reaction chamber is configured to oxidize the mixture and maintainan adiabatic temperature within the reaction chamber above a flameouttemperature of the mixture and a maximum reaction temperature within thereaction chamber below the flameout temperature of the mixture.

In certain embodiments, the oxidizer comprises a heat extractor that isconfigured to remove heat from the reaction chamber. In certainembodiments, the heat extractor is configured to remove heat from thereaction chamber by generating steam. In certain embodiments, thereaction chamber comprises a single inlet. In certain embodiments, theoxidizer is configured to change a flow rate that the mixture isintroduced into the reaction chamber through the single inlet. Incertain embodiments, the heater comprises a heat exchanger thattransfers heat from the reaction products to the mixture at or beforethe one or more inlets. In certain embodiments, the heater is configuredto mix diluents with fuel at or before the one or more inlets. Incertain embodiments, the oxidizer is configured to use heat from thereaction products to generate steam. In certain embodiments, theoxidizer is configured to use heat from the reaction products to drive agenerator for power generation. In certain embodiments, the oxidizer isconfigured to drive a generator by a turbine or a piston engine that isconfigured to expand the reaction products from the reaction chamber. Incertain embodiments, the oxidizer is configured to use heat from thereaction products to heat material that is not passed through theoxidizer. In certain embodiments, the oxidizer is configured to change aflow rate that the reaction products are directed from the reactionchamber through the outlets. In certain embodiments, the oxidizer isconfigured to change a flow rate that one or more of the at least onegas of fuel, oxidants, or diluents is introduced into the reactionchamber through the one or more inlets. In certain embodiments, theoxidizer also includes a regulator that is configured to change at leastone of a flow of the mixture or a pressure of the mixture at or near theinlet.

In certain embodiments, an oxidizer for oxidizing fuel described hereinincludes a reaction chamber having an inlet that is configured to directat least one gas of fuel, oxidants, or diluents, into the reactionchamber and an outlet that is configured to direct reaction productsfrom the reaction chamber, means for maintaining a temperature of themixture, at or before the plurality of inlets, to above an autoignitiontemperature of the mixture, and means for maintaining a temperature ofthe incoming gas, at or before the inlet, to above an autoignitiontemperature of a resulting mixture within the reaction chamber thatcomprises the at least one gas of fuels, oxidants, or diluents, whereinthe reaction chamber is configured to oxidize the mixture and maintainan adiabatic temperature within the reaction chamber above a flameouttemperature of the mixture and a maximum reaction temperature within thereaction chamber below the flameout temperature of the mixture.

In certain embodiments, the reaction chamber comprises a plurality ofinlets. In certain embodiments, the reaction chamber comprises aplurality of outlets. In certain embodiments, the means for raising atemperature comprises a heat exchanger that transfers heat from thereaction products to the mixture at or before the inlet. In certainembodiments, the means for raising a temperature is configured to mixdiluents with fuel at or before the inlet. In certain embodiments, theoxidizer is configured to use heat from the reaction products togenerate steam. In certain embodiments, the oxidizer is configured touse heat from the reaction products to drive a generator for powergeneration. In certain embodiments, the oxidizer is configured to drivea generator by a turbine or a piston engine that is configured to expandthe reaction products from the reaction chamber. In certain embodiments,the oxidizer is configured to use heat from the reaction products toheat material that is not passed through the oxidizer. In certainembodiments, the oxidizer is configured to change a flow rate that themixture is introduced into the reaction chamber through the inlet. Incertain embodiments, the oxidizer is configured to change a flow ratethat the reaction products are directed from the reaction chamberthrough the outlet. In certain embodiments, the oxidizer also includes aregulator that is configured to change at least one of a flow of themixture or a pressure of the mixture at or near the inlet.

In certain embodiments, an oxidizer for oxidizing fuel described hereinincludes a reaction chamber having one or more inlets that areconfigured to direct at least one gas of fuels, oxidants, or diluents,into the reaction chamber and one or more outlets that are configured todirect reaction products from the reaction chamber; and a heater that isconfigured to maintain a temperature of one or more of the at least onegas, at or before the one or more inlets, to below an autoignitiontemperature of a resulting mixture within the reaction chamber thatcomprises the at least one gas of fuel, oxidants, or diluents, whereinand the reaction chamber is configured to oxidize the mixture andmaintain an adiabatic temperature within the reaction chamber below aflameout temperature of the mixture and a maximum reaction temperaturewithin the reaction chamber below the flameout temperature of themixture.

In certain embodiments, the reaction chamber comprises a single inlet.In certain embodiments, the oxidizer is configured to change a flow ratethat the mixture is introduced into the reaction chamber through the oneor more inlets. In certain embodiments, the oxidizer is configured tochange a flow rate that one or more of the at least one gas of fuel,oxidants, or diluents is introduced into the reaction chamber throughthe one or more inlets. In certain embodiments, the oxidizer alsoincludes a heat exchanger that transfers heat from the reaction productsto the mixture at or before the one or more inlets. In certainembodiments, the heater is configured to mix diluents with fuel at orbefore the one or more inlets. In certain embodiments, the oxidizer isconfigured to use heat from the reaction products to generate steam. Incertain embodiments, the oxidizer is configured to use heat from thereaction products to drive a generator for power generation. In certainembodiments, the oxidizer is configured to drive a generator by aturbine or a piston engine that is configured to expand the reactionproducts from the reaction chamber. In certain embodiments, the oxidizeris configured to use heat from the reaction products to heat materialthat is not passed through the oxidizer. In certain embodiments, theoxidizer is configured to change a flow rate that the reaction productsare directed from the reaction chamber through the outlets. In certainembodiments, the oxidizer also includes a regulator that is configuredto change at least one of a flow of the mixture or a pressure of themixture at or near the inlet.

In certain embodiments, an oxidizer for oxidizing fuel described hereinincludes a reaction chamber having an inlet that is configured to directat least one gas of fuel, oxidants, or diluents, into the reactionchamber and an outlet that is configured to direct reaction productsfrom the reaction chamber; and means for maintaining a temperature ofthe incoming gas, at or before the inlet, to below an autoignitiontemperature of a resulting mixture within the reaction chamber thatcomprises the at least one gas of fuel, oxidants, or diluents, whereinthe reaction chamber is configured to oxidize the mixture and maintainan adiabatic temperature within the reaction chamber below a flameouttemperature of the mixture and a maximum reaction temperature within thereaction chamber below the flameout temperature of the mixture.

In certain embodiments, the reaction chamber comprises a plurality ofinlets. In certain embodiments, the reaction chamber comprises aplurality of outlets. In certain embodiments, the means for maintaininga temperature comprises a heat exchanger that transfers heat from thereaction products to the mixture at or before the inlet. In certainembodiments, the means for maintaining a temperature is configured tomix diluents with fuel at or before the inlet. In certain embodiments,the oxidizer is configured to use heat from the reaction products togenerate steam. In certain embodiments, the oxidizer is configured touse heat from the reaction products to drive a generator for powergeneration. In certain embodiments, the oxidizer is configured to drivea generator by a turbine or a piston engine that is configured to expandthe reaction products from the reaction chamber. In certain embodiments,the oxidizer is configured to use heat from the reaction products toheat material that is not passed through the oxidizer. In certainembodiments, the oxidizer is configured to change a flow rate that themixture is introduced into the reaction chamber through the inlet. Incertain embodiments, the oxidizer is configured to change a flow ratethat the reaction products are directed from the reaction chamberthrough the outlet. In certain embodiments, the oxidizer includes aregulator that is configured to change at least one of a flow of themixture or a pressure of the mixture at or near the inlet.

In certain embodiments, an oxidizer for oxidizing fuel described hereinincludes a reaction chamber having one or more inlets that areconfigured to direct at least one gas of fuel, oxidants, or diluents,into the reaction chamber and one or more outlets that are configured todirect reaction products from the reaction chamber, and a heater that isconfigured to maintain a temperature of one or more of the at least onegas, at or before the one or more inlets, to below an autoignitiontemperature of a resulting mixture within the reaction chamber thatcomprises the at least one gas of fuel, oxidants, or diluents, whereinthe reaction chamber is configured to oxidize the mixture and maintainan adiabatic temperature within the reaction chamber above a flameouttemperature of the mixture and a maximum reaction temperature within thereaction chamber below the flameout temperature of the mixture.

In certain embodiments, a heat extractor that is configured to removeheat from the reaction chamber. In certain embodiments, the heatextractor is configured to remove heat from the reaction chamber bygenerating steam. In certain embodiments, the oxidizer also includes aheat conveyor within the reaction chamber that is configured todistribute heat within the reaction chamber. In certain embodiments, theheat conveyor comprises a porous media within the reaction chamber. Incertain embodiments, the heat conveyor comprises a fluid media withinthe reaction chamber. In certain embodiments, the heat conveyorcomprises a media that is circulated through the reaction chamber. Incertain embodiments, the reaction chamber comprises a single inlet. Incertain embodiments, the oxidizer also includes a heat exchanger thattransfers heat from the reaction products to the mixture at or beforethe one or more inlets. In certain embodiments, the heater is configuredto mix diluents with fuel at or before the one or more inlets. Incertain embodiments, the oxidizer is configured to use heat from thereaction products to drive a generator for power generation. In certainembodiments, the oxidizer is configured to drive a generator by aturbine or a piston engine that is configured to expand the reactionproducts from the reaction chamber. In certain embodiments, the oxidizeris configured to use heat from the reaction products to heat materialthat is not passed through the oxidizer. In certain embodiments, theoxidizer is configured to change a flow rate that one or more of the atleast one gas of fuel, oxidants, or diluents is introduced into thereaction chamber through the one or more inlets. In certain embodiments,the oxidizer is configured to change a flow rate that the reactionproducts are directed from the reaction chamber through the outlets. Incertain embodiments, the oxidizer also includes a regulator that isconfigured to change at least one of a flow of the mixture or a pressureof the mixture at or near the inlet.

In certain embodiments, an oxidizer for oxidizing fuel described hereinincludes a reaction chamber having an inlet that is configured to directat least one gas of fuel, oxidants, or diluents, into the reactionchamber and an outlet that is configured to direct reaction productsfrom the reaction chamber, and a heater for maintaining a temperature ofthe incoming gas, at or before the inlet, to below an autoignitiontemperature of a resulting mixture within the reaction chamber thatcomprises the at least one gas of fuel, oxidants, or diluents, whereinthe reaction chamber is configured to oxidize the mixture and maintainan adiabatic temperature within the reaction chamber above a flameouttemperature of the mixture and a maximum reaction temperature within thereaction chamber below the flameout temperature of the mixture.

In certain embodiments, the oxidizer includes means for removing heatfrom the reaction chamber. In certain embodiments, the means forremoving heat is configured to remove heat from the reaction chamber bygenerating steam. In certain embodiments, the oxidizer also includesmeans for distributing heat within the reaction chamber. In certainembodiments, the means for distributing heat comprises a porous mediawithin the reaction chamber. In certain embodiments, the means fordistributing heat comprises a fluid media within the reaction chamber.In certain embodiments, the means for distributing heat comprises amedia that is circulated through the reaction chamber. In certainembodiments, the reaction chamber comprises a plurality of inlets. Incertain embodiments, the reaction chamber comprises a plurality ofoutlets. In certain embodiments, the heater comprises a heat exchangerthat transfers heat from the reaction products to the mixture at orbefore the inlet. In certain embodiments, the heater is configured tomix diluents with fuel at or before the inlet.

In certain embodiments, the oxidizer is configured to use heat from thereaction products to drive a generator for power generation. In certainembodiments, the oxidizer is configured to drive a generator by aturbine or a piston engine that is configured to expand the reactionproducts from the reaction chamber. In certain embodiments, the oxidizeris configured to use heat from the reaction products to heat materialthat is not passed through the oxidizer. In certain embodiments, theoxidizer is configured to change a flow rate that one or more of the atleast one gas of fuel, oxidants, or diluents is introduced into thereaction chamber through the inlet. In certain embodiments, the oxidizeris configured to change a flow rate that the reaction products aredirected from the reaction chamber through the outlet. In certainembodiments, the oxidizer also includes a regulator that is configuredto change at least one of a flow of the mixture or a pressure of themixture at or near the inlet.

In certain embodiments, a system for oxidizing fuel described hereinincludes a first reaction chamber having a first inlet and a firstoutlet, the first reaction chamber being configured to receive a firstgas, comprising an oxidizable fuel, through the first inlet, the firstreaction chamber configured to maintain gradual oxidation of the firstgas and to communicate flue gas through the first outlet; and a secondreaction chamber, separate from the first reaction chamber, having asecond inlet and a second outlet, the second reaction chamber beingconfigured to receive a second gas, comprising an oxidizable fuel, andthe flue gas through the second inlet, the second reaction chamberconfigured to maintain gradual oxidation of the second gas; wherein theflue gas is communicated from the first outlet to the second inlet untilan internal temperature within the second reaction chamber is above anautoignition temperature of the second gas.

In certain embodiments, the flue gas is not communicated from the firstoutlet to the second inlet after the internal temperature is above theautoignition temperature. In certain embodiments, at least one of thefirst or second reaction chambers is configured to reduce a respectiveinternal temperature when the internal temperature within the respectivereaction chamber approaches or exceeds a flameout temperature of therespective fuel. In certain embodiments, at least one of first or secondreaction chambers is configured to reduce the respective internaltemperature by removing heat from the respective reaction chamber. Incertain embodiments, at least one of first or second reaction chambersis configured to remove heat by a heat exchanger. In certainembodiments, the heat exchanger comprises a fluid introduced into therespective reaction chamber. In certain embodiments, the heat exchangeris configured to evacuate the fluid from the respective reactionchamber. In certain embodiments, the heat exchanger comprises a meansfor generating steam. In certain embodiments, the heat exchanger isconfigured to draw heat out of the respective reaction chamber when thetemperature within the respective reaction chamber exceeds 2300° F. Incertain embodiments, the second reaction chamber is configured to mixthe flue gas with the second gas when a temperature of the second gas atthe second inlet approaches or drops below the autoignition temperatureof the second fuel. In certain embodiments, the system also includes aturbine or a piston engine that receives gas from at least one of thereaction chambers. In certain embodiments, the turbine receives andexpands gas from the second reaction chamber. In certain embodiments,the system also includes a compressor that receives and compresses gasprior to introduction of the gas into at least one of the reactionchambers. In certain embodiments, the compressor is configured tocompress the second gas prior to introducing the second gas into thesecond reaction chamber.

In certain embodiments, a system for oxidizing fuel described hereinincludes a first reaction chamber having an outlet, the first reactionchamber being configured to maintain gradual oxidation of a first gas,comprising an oxidizable fuel, and to communicate reaction productsthrough the first outlet; and a second reaction chamber, separate fromthe first reaction chamber, having an inlet that is configured toreceive a second gas, comprising an oxidizable fuel, and the reactionproducts, the second reaction chamber being configured to maintaingradual oxidation of the second gas and to receive the reaction productsfrom the first reaction chamber through the inlet while an internaltemperature within the second reaction chamber is below an autoignitiontemperature of the second gas.

In certain embodiments, the reaction products are not communicated tothe second reaction chamber from the first reaction chamber after theinternal temperature is above the autoignition temperature. In certainembodiments, at least one of the first or second reaction chambers isconfigured to reduce a respective internal temperature when the internaltemperature within the respective reaction chamber approaches or exceedsa flameout temperature of the respective fuel. In certain embodiments,at least one of first or second reaction chambers is configured toreduce the respective internal temperature by removing heat from therespective reaction chamber. In certain embodiments, the second reactionchamber is configured to mix the reaction products with the second gaswhen a temperature of the second gas at the inlet approaches or dropsbelow the autoignition temperature of the second fuel. In certainembodiments, the system also includes a turbine or a piston engine thatreceives gas from at least one of the reaction chambers. In certainembodiments, the turbine receives and expands gas from the secondreaction chamber. In certain embodiments, the system also includes acompressor that receives and compresses gas prior to introduction of thegas into at least one of the reaction chambers. In certain embodiments,the compressor is configured to compress the second gas prior tointroducing the second gas into the second reaction chamber.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet and to maintain an oxidation process;a detection module that detects when a reaction chamber temperature ofthe gas approaches or drops below an autoignition threshold of the gaswithin the reaction chamber, such that the reaction chamber will notoxidize the fuel; and a correction module that outputs instructions,based on the detection module, to change at least one of a residencetime of the gas within the reaction chamber and an autoignition delaytime within the reaction chamber sufficient for the gas to autoigniteand oxidize while within the reaction chamber.

In certain embodiments, the correction module is configured to changethe residence time of the gas within the reaction chamber by alteringflow of the gas through the reaction chamber. In certain embodiments,the correction module is configured to increase the residence time ofthe gas within the reaction chamber by decreasing flow of the gasthrough the reaction chamber. In certain embodiments, the correctionmodule is configured to increase the residence time of the gas withinthe reaction chamber by recirculating flow of the gas from the outlet tothe inlet of the reaction chamber. In certain embodiments, thecorrection module is configured to change the autoignition delay timewithin the reaction chamber by changing a gas temperature within thereaction chamber. In certain embodiments, the correction module isconfigured to decrease the autoignition delay time within the reactionchamber by increasing a gas temperature within the reaction chamber witha heater. In certain embodiments, the correction module is configured todecrease the autoignition delay time within the reaction chamber bycirculating product gas from the outlet to the inlet. In certainembodiments, the reaction chamber is configured to maintain oxidation ofthe oxidizable fuel beneath the flameout temperature without a catalyst.In certain embodiments, the system also includes a turbine or a pistonengine that receives gas from the reaction chamber and expands the gas.In certain embodiments, the system also includes a compressor thatreceives and compresses gas, comprising a fuel mixture, prior tointroduction of the fuel mixture into the reaction chamber. In certainembodiments, the oxidizable fuel comprises at least one of hydrogen,methane, ethane, ethylene, natural gas, propane, propylene, propadiene,n-butane, iso-butane, butylene-1, butadiene, iso-pentane, n-pentane,acetylene, hexane, and carbon monoxide.

In certain embodiments, a system for oxidizing fuel described hereinincludes an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet and to maintain an oxidation process,a detection module that detects when a reaction chamber temperature ofthe gas approaches or drops below an autoignition threshold of the gaswithin the reaction chamber, such that the reaction chamber will notoxidize the fuel, and a correction module that is configured todetermine, with a processor and based on the detection module, a changeto at least one of a residence time of the gas within the reactionchamber and an autoignition delay time within the reaction chambersufficient for the gas to autoignite and oxidize while within thereaction chamber, wherein the oxidizer is configured to, based on thechange to at least one of the residence time and the autoignition delaytime, oxidize the gas while the gas is within the reaction chamber.

In certain embodiments, the correction module is configured to changethe residence time of the gas within the reaction chamber by alteringflow of the gas through the reaction chamber. In certain embodiments,the correction module is configured to increase the residence time ofthe gas within the reaction chamber by decreasing flow of the gasthrough the reaction chamber. In certain embodiments, the correctionmodule is configured to increase the residence time of the gas withinthe reaction chamber by recirculating flow of the gas from the outlet tothe inlet of the reaction chamber. In certain embodiments, thecorrection module is configured to change the autoignition delay timewithin the reaction chamber by changing a gas temperature within thereaction chamber. In certain embodiments, the correction module isconfigured to decrease the autoignition delay time within the reactionchamber by increasing a gas temperature within the reaction chamber witha heater. In certain embodiments, the correction module is configured todecrease the autoignition delay time within the reaction chamber bycirculating product gas from the outlet to the inlet. In certainembodiments, the reaction chamber is configured to maintain oxidation ofthe oxidizable fuel beneath the flameout temperature without a catalyst.

In certain embodiments, a system for oxidizing fuel described hereininclude an oxidizer having a reaction chamber with an inlet and anoutlet, the reaction chamber configured to receive a gas comprising anoxidizable fuel through the inlet and to maintain an oxidation process,and a module that outputs instructions, based on detection of a reactionchamber temperature, to increase at least one of a residence time of thegas within the reaction chamber and a reaction temperature within thereaction chamber, such that the fuel oxidizes while in the reactionchamber.

In certain embodiments, the module is configured to change the residencetime of the gas within the reaction chamber by altering flow of the gasthrough the reaction chamber. In certain embodiments, the module isconfigured to increase the residence time of the gas within the reactionchamber by decreasing flow of the gas through the reaction chamber. Incertain embodiments, the module is configured to increase the residencetime of the gas within the reaction chamber by recirculating flow of thegas from the outlet to the inlet of the reaction chamber. In certainembodiments, the module is configured to decrease the autoignition delaytime within the reaction chamber by increasing a gas temperature withinthe reaction chamber with a heater. In certain embodiments, thecorrection module is configured to decrease the autoignition delay timewithin the reaction chamber by circulating product gas from the outletto the inlet.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of in an oxidation system that receives a gascomprising an oxidizable fuel into a reaction chamber having an inletand an outlet and being configured to maintain an oxidation process,detecting when a reaction chamber temperature of the gas approaches ordrops below a level such that the reaction chamber alone will notsupport oxidation of the fuel, and changing, based on the detectionmodule, at least one of a residence time of the gas within the reactionchamber and an autoignition delay time within the reaction chambersufficient for the gas to autoignite and oxidize while within thereaction chamber.

In certain embodiments, the residence time of the gas is changed withinthe reaction chamber by altering flow of the gas through the reactionchamber. In certain embodiments, the residence time of the gas ischanged within the reaction chamber by decreasing flow of the gasthrough the reaction chamber. In certain embodiments, the residence timeof the gas is changed within the reaction chamber by recirculating flowof the gas from the outlet to the inlet of the reaction chamber. Incertain embodiments, the autoignition delay time within the reactionchamber is changed by changing a gas temperature within the reactionchamber. In certain embodiments, the autoignition delay time isdecreased within the reaction chamber by increasing a gas temperaturewithin the reaction chamber with a heater. In certain embodiments, theautoignition delay time is decreased by circulating product gas from theoutlet to the inlet. In certain embodiments, the reaction chambermaintains oxidation of the oxidizable fuel beneath the flameouttemperature without a catalyst. In certain embodiments, the method alsoincludes the step of expanding product gas from the reaction chamber ina turbine or a piston engine. In certain embodiments, the method alsoincludes the step of compressing the gas prior to introducing the gasinto the reaction chamber. In certain embodiments, the oxidizable fuelcomprises at least one of hydrogen, methane, ethane, ethylene, naturalgas, propane, propylene, propadiene, n-butane, iso-butane, butylene-1,butadiene, iso-pentane, n-pentane, acetylene, hexane, and carbonmonoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the steps of in an oxidation system that receives a gascomprising an oxidizable fuel into a reaction chamber having an inletand an outlet and being configured to maintain an oxidation process,detecting when a reaction chamber temperature of the gas approaches ordrops below a level such that the reaction chamber alone will notsupport gradual oxidation of the fuel, and changing, based on thedetection module, an autoignition delay time within the reaction chambersufficient for the gas to autoignite and oxidize while within thereaction chamber.

In certain embodiments, changing the autoignition delay time comprisesintroducing additional heat into the reaction chamber, therebyincreasing an internal reaction chamber temperature to a level that willmaintain oxidation of the fuel. In certain embodiments, the method alsoincludes the step of changing the residence time of the gas within thereaction chamber by altering flow of the gas through the reactionchamber. In certain embodiments, the method also includes the step ofchanging the residence time of the gas within the reaction chamber bydecreasing flow of the gas through the reaction chamber. In certainembodiments, the method also includes the step of changing the residencetime of the gas within the reaction chamber by recirculating flow of thegas from the outlet to the inlet of the reaction chamber. In certainembodiments, the reaction chamber maintains oxidation of the oxidizablefuel beneath the flameout temperature without a catalyst. In certainembodiments, the method also includes the step of expanding product gasfrom the reaction chamber in a turbine or a piston engine. In certainembodiments, the oxidizable fuel comprises at least one of hydrogen,methane, ethane, ethylene, natural gas, propane, propylene, propadiene,n-butane, iso-butane, butylene-1, butadiene, iso-pentane, n-pentane,acetylene, hexane, and carbon monoxide.

In certain embodiments, a method for oxidizing fuel described hereinincludes the step of maintaining oxidation of an oxidizable fuel byintroducing a heat source into the reaction chamber, thereby increasingan internal reaction chamber temperature to a level that will maintainoxidation of the fuel when a reaction chamber temperature of the gasapproaches or drops below a temperature level such that the reactionchamber alone will not support oxidation of the fuel.

In certain embodiments, increasing the internal temperature decreasesautoignition delay time. In certain embodiments, the method alsoincludes the step of changing the residence time of the gas within thereaction chamber by altering flow of the gas through the reactionchamber. In certain embodiments, the method also includes the step ofchanging the residence time of the gas within the reaction chamber bydecreasing flow of the gas through the reaction chamber. In certainembodiments, the method also includes the step of changing the residencetime of the gas within the reaction chamber by recirculating flow of thegas from the outlet to the inlet of the reaction chamber. In certainembodiments, the reaction chamber maintains oxidation of the oxidizablefuel beneath the flameout temperature without a catalyst. In certainembodiments, the method also includes the step of expanding product gasfrom the reaction chamber in a turbine or a piston engine. In certainembodiments, the oxidizable fuel comprises at least one of hydrogen,methane, ethane, ethylene, natural gas, propane, propylene, propadiene,n-butane, iso-butane, butylene-1, butadiene, iso-pentane, n-pentane,acetylene, hexane, and carbon monoxide.

In certain embodiments, a method of oxidizing a fuel described hereinincludes the steps of mixing a gas having a low-energy-content (LEC)fuel with one or more of the group of a gas comprising ahigh-energy-content (HEC) fuel, a gas comprising an oxidant, and a gascomprising a diluent to form a gas mixture, wherein all of the gases areat temperatures below the autoignition temperature of any of the gasesbeing mixed; increasing the temperature of the gas mixture to at theleast an autoignition temperature of the gas mixture and allowing thegas mixture to autoignite; and maintaining the temperature of the gasmixture below a flameout temperature while the autoignited gas mixtureoxidizes.

In certain embodiments, the gas mixture is raised to at least theautoignition temperature by a heat exchanger. In certain embodiments,the heat exchanger is positioned within a reaction chamber thatmaintains oxidation of the gas mixture without a catalyst. In certainembodiments, the gas mixture is raised to at least the autoignitiontemperature within a reaction chamber that maintains oxidation of thegas mixture without a catalyst. In certain embodiments, the reactionchamber maintains oxidation of the mixture beneath a flameouttemperature of the gas mixture. In certain embodiments, the method alsoincludes the step of expanding gas with a turbine or a piston enginethat receives the gas from the reaction chamber. In certain embodiments,the gas mixture comprises at least one of hydrogen, methane, ethane,ethylene, natural gas, propane, propylene, propadiene, n-butane,iso-butane, butylene-1, butadiene, iso-pentane, n-pentane, acetylene,hexane, and carbon monoxide.

In certain embodiments, a method of oxidation described herein includesthe steps of heating a gas comprising an oxidant to at the least anauto-ignition temperature of a first gas mixture comprising a gas withan oxidant mixed with determined ranges of a low-energy-content (LEC)fuel and a high-energy-content (HEC) fuel; injecting, after the heating,a second gas mixture of the LEC fuel gas and the HEC fuel, wherein theratio of the LEC and HEC gas and the rate of injection are selected toproduce substantially the same first gas mixture ratios when injectedinto the heated gas containing an oxidant; mixing the injected secondgas with the heated gas containing an oxidant at a rate to produce asubstantially homogeneous first gas mixture in a time less than theignition delay time for the second gas mixture and allowing the firstgas mixture to auto-ignite; and maintaining the temperature of the firstgas mixture below a flameout temperature while the auto-ignited firstgas mixture oxidizes.

In certain embodiments, the first gas mixture is raised to at least theautoignition temperature by a heat exchanger. In certain embodiments,the heat exchanger is positioned within a reaction chamber thatmaintains oxidation of the first gas mixture without a catalyst. Incertain embodiments, the first gas mixture is raised to at least theautoignition temperature within a reaction chamber that maintainsoxidation of the gas mixture without a catalyst. In certain embodiments,the reaction chamber maintains oxidation of the second gas mixturebeneath a flameout temperature of the gas mixture. In certainembodiments, the method also includes the step of expanding gas with aturbine or a piston engine that receives the gas from the reactionchamber. In certain embodiments, the first gas mixture comprises atleast one of hydrogen, methane, ethane, ethylene, natural gas, propane,propylene, propadiene, n-butane, iso-butane, butylene-1, butadiene,iso-pentane, n-pentane, acetylene, hexane, and carbon monoxide. Incertain embodiments,

In certain embodiments, a method of oxidization described hereinincludes the steps of receiving into a reaction chamber, via a chamberinlet, the inlet configured to accept a gas having a mixture of alow-energy-content (LEC) fuel and at least one of the group of ahigh-energy-content (HEC) fuel, an oxidant-comprising (OC) gas, and adiluent-containing (DC) gas, the gas mixture being at a temperaturebelow an auto-ignition temperature of the gas mixture; maintaining aninternal temperature of the reaction chamber below a flameouttemperature by heat exchange media disposed within the reaction chamber,maintaining a reaction chamber inlet temperature of the fuel to begreater than an autoignition temperature of the fuel by transferringheat through the heat exchange media, and directing gas entering theinlet through a first path through media that is hotter than anauto-ignition temperature of the gas mixture until the gas mixturereaches a temperature above the auto-ignition temperature of the gasmixture; and directing the gas through a second path through the mediato a chamber outlet, the second path being generally opposite to thefirst flow path.

In certain embodiments, the reaction chamber maintains oxidation of thegas mixture without a catalyst. In certain embodiments, the reactionchamber maintains oxidation of the mixture beneath a flameouttemperature of the gas mixture by circulating the heat exchange mediaoutside the reaction chamber. In certain embodiments, the method alsoincludes the step of expanding gas with a turbine or a piston enginethat receives the gas from the reaction chamber outlet. In certainembodiments, the gas mixture comprises at least one of hydrogen,methane, ethane, ethylene, natural gas, propane, propylene, propadiene,n-butane, iso-butane, butylene-1, butadiene, iso-pentane, n-pentane,acetylene, hexane, and carbon monoxide.

In certain embodiments, an oxidizer described herein includes a reactionchamber having an inlet and an outlet, the inlet configured to accept agas having a mixture of a low-energy-content (LEC) fuel and at least oneof the group of a high-energy-content (HEC) fuel, an oxidant-comprising(OC) gas, and a diluent-containing (DC) gas, the gas mixture being at atemperature below an auto-ignition temperature of the gas mixture; aheat exchange media disposed within the reaction chamber, the mediaconfigured to maintain an internal temperature of the reaction chamberbelow a flameout temperature and to maintain a reaction chamber inlettemperature of the fuel to be greater than an autoignition temperatureof the fuel; and at least one flow path through the chamber from theinlet to the outlet, the flow path configured to direct the gas enteringthe inlet through a first path through media that is hotter than anauto-ignition temperature of the gas mixture until the gas mixturereaches a temperature above the auto-ignition temperature of the gasmixture, whereupon the flow path is further configured to direct theoxidizing gas mixture through a second path through the media to theoutlet, the second path being generally opposite to the first flow path.

In certain embodiments, the reaction chamber is configured to maintainoxidation of the gas mixture along at least one of the first and secondflow paths without a catalyst. In certain embodiments, the reactionchamber is configured to maintain oxidation of the mixture beneath theflameout temperature of the gas mixture by circulating heat exchangemedia outside the reaction chamber. In certain embodiments, the systemalso includes at least one of a turbine or a piston engine that isconfigured to receive gas from the reaction chamber outlet and expandthe gas. In certain embodiments, the gas mixture comprises at least oneof hydrogen, methane, ethane, ethylene, natural gas, propane, propylene,propadiene, n-butane, iso-butane, butylene-1, butadiene, iso-pentane,n-pentane, acetylene, hexane, and carbon monoxide.

In certain embodiments, an oxidizer described herein includes a reactionchamber having an inlet and an outlet, the inlet configured to accept agas having a mixture of a low-energy-content (LEC) fuel and at least oneof the group of a high-energy-content (HEC) fuel, an oxidant-comprising(OC) gas, and a diluent-containing (DC) gas, the gas mixture being at atemperature below an auto-ignition temperature of the gas mixture; and aheat controller that is configured to increase a temperature of the gasmixture to at the least an autoignition temperature of the gas mixture,thereby permitting the gas mixture to autoignite and to maintain thetemperature of the gas mixture below a flameout temperature while theautoignited gas mixture oxidizes.

In certain embodiments, the heat controller comprises a heat exchangerthat is configured to raise the temperature of the mixture to at leastthe autoignition temperature. In certain embodiments, the heat exchangeris positioned within the reaction chamber. In certain embodiments, theheat exchanger is configured to heat the mixture to above theautoignition temperature after the mixture is within the reactionchamber. In certain embodiments, the reaction chamber is configured tomaintain oxidation of the mixture beneath a flameout temperature of thegas mixture without a catalyst. In certain embodiments, the system alsoincludes at least one of a turbine or a piston engine that receives gasfrom the reaction chamber and expands the gas. In certain embodiments,the gas mixture comprises at least one of hydrogen, methane, ethane,ethylene, natural gas, propane, propylene, propadiene, n-butane,iso-butane, butylene-1, butadiene, iso-pentane, n-pentane, acetylene,hexane, and carbon monoxide.

In certain embodiments, an oxidizer described herein includes a reactionchamber having an inlet and an outlet, the inlet configured to accept agas having a mixture of a low-energy-content (LEC) fuel and at least oneof the group of a high-energy-content (HEC) fuel, an oxidant-comprising(OC) gas, and a diluent-containing (DC) gas, the gas mixture being at atemperature below an auto-ignition temperature of the gas mixture; aheat controller that is configured to heat the gas to at the least anauto-ignition temperature of a first gas mixture, comprising a gas withan oxidant mixed with determined ranges of a low-energy-content (LEC)fuel and a high-energy-content (HEC) fuel; an injector that isconfigured to inject, after the first gas is heated to at the least anauto-ignition temperature of a first gas mixture, a second gas mixtureof the LEC fuel gas and the HEC fuel, wherein the injector injects aratio of the LEC and HEC gas and at a rate of injection that is selectedto produce substantially the same ratio of LEC and HEC gas as the firstgas mixture when the gas is injected into the reaction chamber, whereinthe reaction chamber is configured to mix the injected second gas withthe heated gas containing an oxidant at a rate to produce asubstantially homogeneous first gas mixture in a time less than theignition delay time for the second gas mixture and allowing the firstgas mixture to auto-ignite and to maintain the temperature of the firstgas mixture below a flameout temperature while the auto-ignited firstgas mixture oxidizes.

In certain embodiments, the heat controller comprises a heat exchangerthat is configured to raise the temperature of the mixture to at leastthe autoignition temperature. In certain embodiments, the heat exchangeris positioned within the reaction chamber. In certain embodiments, thereaction chamber is configured to maintain oxidation of the first gasmixture within the reaction chamber without a catalyst. In certainembodiments, the reaction chamber is configured to maintain oxidation ofthe second gas mixture beneath a flameout temperature of the gas mixturewithout a catalyst. In certain embodiments, the system also includes atleast one of a turbine or a piston engine that is configured to receivegas from the reaction chamber and to expand the gas. In certainembodiments, the first gas mixture comprises at least one of hydrogen,methane, ethane, ethylene, natural gas, propane, propylene, propadiene,n-butane, iso-butane, butylene-1, butadiene, iso-pentane, n-pentane,acetylene, hexane, and carbon monoxide.

The details of one or more embodiments of these concepts are set forthin the accompanying drawings and the description below. Other features,objects, and advantages of these concepts will be apparent from thedescription and drawings, and from the claims. As described hereinvarious embodiments referenced above or described below may be usedtogether and in conjunction with other embodiments described orsuggested herein. The separate discussion of different embodimentsshould not be construed, unless otherwise clearly described, as meaningthat the embodiments are distinct or cannot be combined, as embodimentsdescribed in one portion, figure, section, or paragraph can be combinedwith other embodiments described elsewhere.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide furtherunderstanding and are incorporated in and constitute a part of thisspecification, illustrate disclosed embodiments and together with thedescription serve to explain the principles of the disclosedembodiments.

FIG. 1-1A is a schematic representation of a conventional fired orsupplemental-fired oxidizer system for disposing of a waste streamcontaining VOCs.

FIG. 1-1B is a schematic representation of a conventional catalyticoxidizer system.

FIG. 1-1C is a schematic representation of a conventional oxidizersystem that includes a recuperator.

FIG. 1-1D is a schematic representation of a conventional regenerativeoxidizer system.

FIG. 1-2A is a diagram of the ignition energy of an air-methane mixture.

FIG. 1-2B is a diagram of the reaction temperatures of variouscombustion and oxidation processes.

FIG. 1-3 is a diagram of the gradual oxidation of a pre-mixed air-fuelmixture according to certain aspects of the present disclosure.

FIG. 1-4A is a diagram of the gradual oxidation of a fuel mixture wheninjected into pre-heated air according to certain aspects of the presentdisclosure.

FIG. 1-4B is a diagram of the gradual oxidation process used to heat anexternal fluid according to certain aspects of the present disclosure.

FIG. 1-4C is a diagram of a multi-stage gradual oxidation processaccording to certain aspects of the present disclosure.

FIG. 1-5 is a flow chart of an exemplary gradual oxidation process of apre-mixed air-fuel mixture according to certain aspects of the presentdisclosure.

FIG. 1-6 is a flow chart of an exemplary gradual oxidation process of afuel mixture that is injected into pre-heated air according to certainaspects of the present disclosure.

FIG. 1-7 is a schematic diagram of an exemplary pre-mix oxidation systemaccording to certain aspects of the present disclosure.

FIG. 1-8 is a schematic diagram of an exemplary injection gradualoxidation system according to certain aspects of the present disclosure.

FIG. 1-9 is a schematic representation of an exemplary turbine-drivenpower-generation system according to certain aspects of the presentdisclosure.

FIG. 1-10 is a schematic representation of another turbine-drivenpower-generation system according to certain aspects of the presentdisclosure.

FIG. 1-11 is a cutaway view of an exemplary GO reaction chamber withdirect fuel or air-fuel mixture according to certain aspects of thepresent disclosure.

FIG. 1-12 schematically depicts the flow through a gradual oxidationsystem having a sparger according to certain aspects of the presentdisclosure.

FIG. 1-13 is a schematic representation of a multi-stage GO reactionchamber according to certain aspects of the present disclosure.

FIG. 1-14 is a schematic representation of a fluidized bed GO reactionchamber according to certain aspects of the present disclosure.

FIG. 1-15A is a schematic representation of a recirculating bed GOreaction chamber according to certain aspects of the present disclosure.

FIG. 1-15B is a schematic representation of another recirculating bed GOreaction chamber according to certain aspects of the present disclosure.

FIG. 1-16 is a schematic representation of a GO reaction chamber withflue gas recirculation according to certain aspects of the presentdisclosure.

FIGS. 1-17A and 17B depict a GO reaction chamber with structuredreaction elements according to certain aspects of the presentdisclosure.

FIG. 2-1 is a schematic representation of an oxidizer coupled to a heatexchanger to provide process heating to an industrial process accordingto certain aspects of the present disclosure.

FIG. 2-2 is a schematic representation of an oxidizer coupled to aheating chamber to heat a process material according to certain aspectsof the present disclosure.

FIG. 2-3 is a schematic representation of an oxidizer comprising aninternal heat exchanger through which a process gas passes according tocertain aspects of the present disclosure.

FIG. 2-4 is a schematic representation of another embodiment of anoxidizer comprising a plurality of internal heat exchangers throughwhich a process gas passes according to certain aspects of the presentdisclosure.

FIG. 2-5 is a schematic representation of an oxidizer comprising aplurality of gradual oxidation zones with adjoining reaction zoneswherein batches of a process material are heated according to certainaspects of the present disclosure.

FIG. 2-6 is a schematic representation of an oxidizer comprising aplurality of gradual oxidation zones with adjoining reaction zoneswherein continuous flows of a process material are heated according tocertain aspects of the present disclosure.

FIGS. 2-7A and 2-7B are a perspective view and a cross-section view ofan example design detail of an oxidizer element according to certainaspects of the present disclosure.

FIG. 2-8 is a plot of the temperatures with the oxidizer of FIGS. 2-7Aand 2-7B according to certain aspects of the present disclosure.

FIG. 2-9 is a perspective view of an oxidizer assembly using theoxidizer element of FIGS. 2-7A and 2-7B according to certain aspects ofthe present disclosure.

FIG. 3-1 is a schematic of an exemplary Schnepel cycle power generationsystem according to certain aspects of the present disclosure.

FIG. 3-2 is a conceptual depiction of the power generation system ofFIG. 3-1 according to certain aspects of the present disclosure.

FIGS. 3-3 to 3-10 are schematic representation of additional embodimentsof Schnepel cycle power generation systems according to certain aspectsof the present disclosure.

FIG. 4-1 is a three-stage gradual oxidizer fluid heater system accordingto certain aspects of the present disclosure.

FIG. 4-2 is another embodiment of a three-stage gradual oxidizer fluidheater system according to certain aspects of the present disclosure.

FIG. 4-3 is another embodiment of a single-stage recuperative fluidheating system according to certain aspects of the present disclosure.

FIG. 4-4 is another embodiment of a two-stage water-tube type of steamgeneration system according to certain aspects of the presentdisclosure.

FIG. 4-5 is another embodiment of a two-stage fire-tube type of fluidheating system according to certain aspects of the present disclosure.

FIG. 4-6 schematically depicts the flow through a gradual oxidationsystem, which generates steam, having a sparger according to certainaspects of the present disclosure.

FIG. 5-1 is a schematic diagram of an exemplary gradual oxidation systemincorporating steam generation and additional fuel injection accordingto certain aspects of the present disclosure.

FIG. 5-2 is a schematic diagram of an exemplary gradual oxidation systemincorporating steam generation and cogeneration according to certainaspects of the present disclosure.

FIG. 5-3 is a schematic diagram of an exemplary gradual oxidation systemincorporating dual compressors with intercooling according to certainaspects of the present disclosure.

FIG. 5-4 is a schematic diagram of an exemplary gradual oxidation systemincorporating a starter gradual oxidizer according to certain aspects ofthe present disclosure.

FIG. 5-5 is a schematic diagram of an exemplary gradual oxidation systemincorporating multiple points of water injection according to certainaspects of the present disclosure.

FIG. 5-6 is a diagram of the typical gas content of the exhaust ofvarious systems.

DETAILED DESCRIPTION

The following description discloses embodiments of a system foroxidation of a gas that comprises an oxidizable fuel. In certainembodiments, the system includes an oxidizer that can operate togradually oxidize fuel while maintaining a temperature within theoxidizer below a flameout temperature, so that formation of undesirablepollutants, e.g., nitrogen oxide (NOx) and carbon monoxide (CO), issignificantly limited. The fuel desirably enters the oxidizer at or nearan autoignition temperature of the fuel. The system is particularlyadapted for utilization of a fuel with low energy content, such as amethane content below 5%, in a sustainable gradual oxidation process todrive a turbine that further drives a power generator as well as drivinga compressor in the system.

In the following detailed description, numerous specific details are setforth to provide an understanding of the present disclosure. It will beapparent, however, to one ordinarily skilled in the art that embodimentsof the present disclosure may be practiced without some of the specificdetails. In other instances, well-known structures and techniques havenot been shown in detail so as not to obscure the disclosure.

Certain embodiments of methods and systems disclosed herein arepresented in terms of a turbine system that drives a power generatorusing a low-energy-content fluid, such as a methane-containing gas, as aprimary fuel and a higher-energy-content fluid, such as natural gas orcommercial propane, as an auxiliary fuel. Nothing in this disclosureshould be interpreted, unless specifically stated as such, to limit theapplication of any method or system disclosed herein to a particularprimary or auxiliary fuel or a turbine system of this particularconfiguration. Other configurations of turbine-compressor systems areknown to those of skill in the art can be used, and the components andprinciples disclosed herein can be applied to these other systems.

Certain embodiments of methods and systems disclosed herein arepresented in terms of an oxidizer coupled to a reciprocating-pistonsystem that drives a power generator. Nothing in this disclosure shouldbe interpreted, unless specifically stated as such, to limit theapplication of any method or system disclosed herein with respect to aturbine system, such as the use of an auxiliary fuel during a portion ofthe operation, from application to a reciprocating-piston system or acombination of reciprocating-piston and turbine systems.

Certain embodiments of methods and systems disclosed herein arepresented in terms of integrated process equipment that utilizes a GOprocess separately or integrally with material processing functions.Nothing in this disclosure should be interpreted, unless specificallystated as such, to limit the application of any method or systemdisclosed herein with respect to a turbine system orreciprocating-piston system, such as the use of an auxiliary fuel duringa portion of the operation, from application to integrated processequipment or a combination of one or more of the reciprocating-pistonsystems, turbine systems, and integrated process equipment.

Within this document, the term “NOx” refers to a group of oxides ofnitrogen that includes nitric oxide and nitrogen dioxide (NO and NO2).There are at least three commonly acknowledged processes that form NOx.“Thermal NOx” is formed when oxygen and nitrogen present in thecombustion air dissociate in the high temperature area of the combustionzone and subsequently react to form oxides of nitrogen. “Prompt NOx” isformed in the proximity of the flame front as fuel fragments attackmolecular nitrogen to form products such as HCN and N, which are thenoxidized to form NOx. “Fuel NOx” is formed by fuel compounds containingnitrogen, e.g., amines and cyano species, when fuels containing nitrogenare burned. Diatomic nitrogen (N2) is not considered a fuel-boundnitrogen that will generate fuel NOx.

Within this document, the term “flammable” refers to a characteristic ofa material wherein the material will combine with oxygen in anexothermic self-sustaining or self-propagating reaction when thematerial and oxygen are present within a defined range of relativeamounts. It may require an initiating event, such as a spark or flame,to initiate the exothermic reaction.

Within this document, the terms “lower flammability limit” (LFL),sometimes called the “lower explosive limit,” and “upper flammabilitylimit” (UFL), sometimes called the “rich flammability limit” or “upperexplosion limit,” refer to the volumetric fuel concentration where aflame can exist. Concentrations below the LFL or above the UFL will notcause a flame reaction to sustain or propagate.

Within this document, the term “low-energy-content fuel” (LEC fuel)refers to a gas that comprises a flammable gas as a secondary componentand an inert gas as a primary component. A non-limiting example of anLEC fuel is the methane-containing gas that is emitted from a landfillor other waste disposal site. For example, LEC methane gas typicallycontains less than about 30% methane, but may contain as low as 1-5%methane.

Within this document, the term “high-energy-content fuel” (HEC fuel)refers to a gas that comprises a flammable gas as a primary component.HEC fuel may contain secondary components that are naturally mixed withthe primary component, inert, or cannot be economically removed. Anon-limiting example of a HEC fuel is “commercial propane,” thecomposition of which varies locally, but generally contains >85% propane(C₃H₈) and allows up to 10% propylene, up to 10% ethane (C₂H₈), up to2.5% butane (C₄H₁₀) and heavier hydrocarbons, and may include ˜0.01% ofan odorant, usually ethyl mercaptan. A second non-limiting example of aHEC fuel is “natural gas,” wherein a typical unrefined composition maycontain as little as 70% methane and a combined 20% or more of ethane,propane, and butane as well as smaller amounts of carbon dioxide (CO2),oxygen (O2), nitrogen (N2), and hydrogen sulfide (H2S). A thirdnon-limiting example is a landfill gas comprising more than about 50%methane with the balance CO2, N2, and a little O2.

Within this document, the term “oxidant” refers to a gas that comprisessufficient oxygen to support combustion or oxidation of a flammablefuel. A nonlimiting example of an oxidant is ambient air.

Within this document, the term “diluent” refers to a generally inertgas. Nonlimiting examples of a diluent are commercial CO2, N2, and H2O.Diluents can be present in the oxidation products or the fuel reactants.

Within this document, the term “generally inert” is used to refer to amaterial or mixture that does not contain enough flammable material oroxygen to support combustion or oxidation when mixed with either oxygenor fuel when supplied with an ignition source.

Within this document, the term “combustible concentration” refers to theamount of flammable material present in a mixture, wherein theconcentration is usually expressed in terms of a ratio of the flammablematerial in a mixture to the total gas.

Within this document, the term “gradual oxidation” refers to a processwhere a material combines with oxygen in an exothermic reaction whilethe material remains below a determined temperature during the entireprocess. A non-limiting example of such a determined temperature is2300° F., wherein oxidation processes that stay below this temperaturewill not form generally significant amounts of NOx with respect to airpollution regulations and standards.

Within this document, the term “air-fuel mixture” refers to a mixture ofa combustible fuel and an oxidant, and preferably to a gaseous mixturecomprising air. An air-fuel mixture is considered to be generallyhomogeneous unless stated otherwise. In certain circumstances, an LEC orHEC fuel is mixed with ambient air to form an air-fuel mixture. Incertain circumstances, an LEC fuel may contain sufficient oxygen andfuel to be considered an air-fuel mixture without the further additionof air or fuel.

Within this document, the term “autoignition” refers to the spontaneousinitiation of an oxidation or combustion process in a mixture comprisingflammable material and an oxidant. The autoignition temperature is theminimum temperature at which an oxidation or combustion process willoccur in the absence of an ignition source and may depend on thepressure and/or the oxygen and fuel concentrations of the mixture.

Within this document, the term “autoignition delay time” refers to theamount of time a for a mixture, at a temperature above the autoignitiontemperature, to oxidize and release the majority of its exothermicenergy. By way of illustration, methane has an autoignition temperatureof about 1000° F. If a mixture of methane and air is raised to 1000° F.,then it will eventually react to produce H2O and CO2. However, if thissame mixture is brought up to a higher temperature, for example 1200°F., then the ignition delay time might be 2 seconds. If the mixture isbrought up to 1400° F., then the delay might be 100 milliseconds.Autoignition delay time is generally exponentially faster with highertemperatures, and is a function of fuel and oxygen concentrations.Autoignition delay times can be calculated with chemical kineticsoftware programs using complex kinetic mechanisms that can includehundreds of reactions and tens of molecular and radial species.

Within this document, the term “premixed” refers to mixing of air andflammable material, such as an LEC or HEC fuel, to form a generallyhomogeneous air-fuel mixture prior to introducing the mixture into achamber in which oxidation or combustion will take place.

Within this document, the terms “short residence time” is definedrelative to combustion apparatus such as conventional combustionengines, gas turbine combustors, reciprocating engines, burners forboilers, etc. In these conventional combustors, the combustion processis completed within a time period that is typically well below 1 second,usually below 100 milliseconds, and can be below 10 milliseconds. Aprocess having a residence time closer to 1 second, or exceeding 1second, is termed as having a “long residence time.”

Within this document, the term “volatile organic compound” (VOC) refersto organic compounds that will enter a gas phase when at a temperaturein the range of 40-120° F. and may combine with oxygen in an exothermicreaction. Examples of VOCs include, but are not limited to, acetone,acrolein, acrylonitrile, allyl alcohol, allyl chloride, benzene,butene-1, chlorobenzene, 1-2 dichloroethane, ethane, ethanol, ethylacrylate, ethylene, ethyl formate, ethyl mercaptan, methane, methylchloride, methyl ethyl ketone, propane, propylene, toluene,triethylamine, vinyl acetate, and vinyl chloride.

Within this document, the term “maximum reaction temperature” “refers tothe maximum temperature of the chemical oxidation reaction, whichincludes heat transfer or work losses or additions. For example, if heatis removed simultaneously while the reaction occurs, the maximumreaction temperature will be less that the adiabatic reactiontemperature. Similarly, the maximum reaction temperature can be higherthan the adiabatic reaction temperature if heat is added.

Within this document, “flame strain rate” or “flame stretch” refers tocoupling of the turbulent straining of the flame front, either bystretching or curvature, that removes heat from the flame front. Highrates of flame stretch can be created with strong shear layers, and ifthe strain rate is high enough, can extinguish a flame.

Within this document, the term “adiabatic reaction temperature” refersto the temperature that results from a complete chemical oxidationreaction that occurs without any work, heat transfer, or changes inkinetic or potential energy. This is sometimes referred to as aconstant-volume adiabatic reaction temperature.

Within this document, the term “flameout temperature” refers to thetemperature of a substantially uniformly mixed air-fuel mixture belowwhich a flame will not propagate through the mixture. In some instances,by way of example and as shown herein, the flameout temperature may beequivalent to the LFL at any particular temperature of the air-fuelmixture.

Gradual Oxidation

FIG. 1-2A is a diagram of the ignition energy for an air-methanemixture. A mixture of methane and air is flammable in the range ofapproximately 5-15%, by volume, of methane. A stoichiometric mixture ofmethane and air, i.e., a mixture having precisely enough oxygen tocombine with the methane, is approximately 9.5%, by volume. FIG. 1-2Ashows that a stoichiometric air-methane mixture 55 requires the leastignition energy and that increased energy is needed at lower and highermethane concentrations to ignite the mixture.

FIG. 1-2B is a diagram of the reaction temperatures of variouscombustion and oxidation processes, as depicted by system 60. In Zone 1,the combustion must be propagated by an energy source. With a flowingsource of mixture, as typical in combustion devices, the energy sourceto stabilize combustion must be relatively constant with respect totime. This energy source is typically created by creating a hot localpocket of hot combustion products in a recirculation zone. These zonesare created behind bluff bodies or other geometric features (V-gutters,corner recirculation zones). A second method is to swirl a portion ofthe mixture sufficiently such that “vortex breakdown” occurs, and arecirculation zone is formed inside or behind the swirling mixture.These types of flame stabilization techniques are well-known in thecombustion art. The hot recirculation zone serves as a continuousignition source to keep the premixed fuel and air mixture in Zone 1constantly burning.

In Zone 2 of FIG. 1-2B, a flame, even when initiated by a spark or otherignition source, will not propagate through an air-fuel mixture. Theuniform air-fuel mixture is too lean to burn. One method to react apremixed air-fuel mixture in this zone is to lower the activation energyof the reaction with a catalyst. Another method is to provide a locallyricher mixture within the combustion chamber. This locality would have acombustible concentration, and therefore reaction temperaturesconsistent with Zone 1. This richer mixture burns and keeps a flamewithin the combustion chamber, however, propagating the reaction intothe lean regions within the combustion chamber will not occur by flamepropagation and will have to be performed using gas mixing techniques.

Zone 1 and Zone 2 are separated by a line indicating the flameouttemperature over a range of temperatures. One cannot maintain a flamewith a premixed fuel concentration that results in an adiabatic reactiontemperature below this line. To expand on this, if one starts with apremixed flame in Zone 1 and slowly reduces the fuel concentration, theflame temperature, which in this case is the maximum reactiontemperature shown as the Y-axis of FIG. 1-2, will decrease. When thetemperature approaches the flameout temperature line, the flame will beextinguished.

A homogeneous air-fuel mixture in Zone 3 of FIG. 1-2B will autoigniteand react relatively quickly. The challenge of this “flamelesscombustion” quadrant is to uniformly mix the fuel and air and bring themixture to the desired temperature before the air-fuel mixture ignites.For example, if one mixes the fuel and air at a temperature below theautoignition limit, as designated by point “62” in Zone 1, then anyunplanned spark will ignite the mixture while still in Zone 1. Inaddition, once the air-fuel mixture is fully mixed at point “62”, theair-fuel mixture is heated to point “64” by, for example, a heatexchanger or other heating method.

Practitioners of flameless combustion avoid the challenge of mixing atlow temperatures without combustion by mixing the fuel with hot air inZone 3. To prevent ignition from occurring prior to reaching a uniformmixture, the autoignition is delayed by the use of one of twotechniques. One technique is to inject the fuel into a mixture of airand recirculated flue gas. The flue gas has, relative to air, excess CO2and H2O and a reduced amount of O2. The reduced O2 concentration willdelay autoignition, thereby permitting the mixture of the fuel with theair-flue gas mixture to reach a generally homogeneous composition.

A second technique is to induce “flame strain rate” or “flame stretch”to delay autoignition. Strained flames are flames that occur in highlyturbulent flows with strong shear layers. They create aturbulent-chemistry interaction which delays reactions and, in extremecases, can extinguish flames. To implement flame stretch, the fuel isinjected into a turbulent air flow, e.g. the air is emitted from anozzle at a high velocity and the fuel is injected into the stream ofemitted air. The air-fuel mixture reaches a generally homogeneouscomposition before the flow of the air-fuel mixture becomesnon-turbulent, and flame stretch causes the delay of autoignition duringthis mixing period. It is possible to combine the two techniques andinject the fuel into a jet of an oxidant that comprises a mixture of airand recirculated flue gas, thereby delaying the autoignition of theoxidant-fuel mixture by both a reduction in the O2 concentration andflame stretch, thereby achieving a distributed reaction throughout thechamber.

One aspect of the flame structure in Zone 1 is that the oxidationreaction takes place in a relatively narrow reaction zone, called theflame front. In this locality, heat from the post-combustion zone andchemical radicals from the flame are diffusing, both molecularly andturbulently, into the unreacted gases. In Zone 2, reaction occurslocally near the catalyst, and is termed heterogeneous combustion. OnlyZones 3 and 4 are capable of a volumetrically-distributed reaction dueto the autoignition initiating the reaction, as opposed to thermalfeedback from an existing flame.

Zone 4 is the region wherein the fuel concentration is too low tosustain a flame, i.e. below the flameout temperature line, and hotenough to autoignite. Gradual oxidation is suitable for the oxidation offuels in this zone. In contrast to Zones 1-2, reactions in Zone 4 mayoccur relatively uniformly within the entire reactor/combustor volumewith no well-defined ‘reaction flame front.’

FIG. 1-3 is a schematic diagram of an exemplary gradual oxidationprocess according to certain aspects of the present disclosure. FIG. 1-3shows the various regions, numbered 72, 74, 75, 76 a, 76 b, and 78, offlame reaction behavior for a homogenous air-fuel mixture at a constantpressure. The ordinate is the temperature of the air-fuel mixture andthe abscissa is the concentration of fuel in the air-fuel mixture. TheLFL becomes lower, i.e., a leaner combustible concentration, as thetemperature of the air-fuel mixture increases. The UFL becomes higher,i.e. a richer combustible concentration, as the temperature increases.It can be seen that a wider range of combustible concentrations becomesflammable as the temperature increases.

Zone 72 is a region where a mixture will not autoignite, but a flamewill propagate through the air-fuel mixture after the introduction of asufficient energy source. The usual form of energy introduction is aspark from a spark plug or igniter, although other devices such as glowplugs or ionized plasmas could be used.

Zone 74 lies below the LFL and below the autoignition temperature. Inthis region, a flame, even if initiated by a spark, will not propagatethrough the mixture.

Zone 76 is broken into two zones 76 a and 76 b to account for the timeto complete the reaction. If a spark occurs within Zones 76 a or 76 b, aflame will be initiated and will propagate through the air-fuel mixture.Air-fuel mixtures in Zones 76 a or 76 b may also autoignite because theenergy contained by the air-fuel mixture at these temperatures exceedsthe activation energy of the air-fuel mixture, as previously discussedwith respect to FIG. 1-2B. The minimum temperature at which a mixturewill autoignite, given enough time, is known as the autoignitiontemperature (AIT). Zone 76 is bounded by the AIT and the UFL and LFL,and any mixture having a combustible concentration and a temperaturewithin Zone 76 b or 76 a will autoignite. Combustion of air-fuelmixtures in Zone 76 a will autoignite and react in a timeframe shorterthan a short residence time. Air-fuel mixtures at combustibleconcentrations and temperatures in Zone 76 b will also autoignite andreact, but will react in a timeframe consistent with a long residencetime.

In Zone 78, a spark or other energy source will not initiate a flame norwill a flame propagate through the air-fuel mixture. It is possible tooxidize the fuel through autoignition by allowing enough time for theoxidation reactions to complete. The time for these reactions in Zone 78is consistent with a long residence time.

Zone 75 is irrelevant to most combustion devices. A flame cannotpropagate through an air-fuel in Zone 75 as the combustible compositionis too rich. If an oxidation process were to be initiated in the portionof Zone 75 that is above the autoignition temperature, there is notenough air to complete the oxidation of the fuel and the oxidationprocess will self-extinguish, resulting in unburned fuel being exhaustedfrom the combustion device.

In certain aspects, a process starting at point 80 heats an air-fuelmixture to a temperature above an autoignition temperature of theair-fuel mixture, indicated by point 82. A reaction chamber, such asreaction chamber 500 of FIG. 1-11, is configured to oxidize the air-fuelmixture and maintain an adiabatic temperature and a maximum reactiontemperature in the reaction chamber below the flameout temperature ofthe air-fuel mixture, as indicated by the dashed line connecting points82 and 84 remaining below the LFL.

FIG. 1-4A is a diagram of the gradual oxidation of a fuel mixture wheninjected into pre-heated air according to certain aspects of the presentdisclosure. In this process, ambient air at point “92” in Zone 74 isheated by various means (heat exchange, compression) to point “94” inZone 78. Fuel, which may be LEC fuel, diluted HEC fuel, or a mixture ofHEC and LEC fuels, is then added to the hot air, thereby moving theair-fuel mixture from point “94” to point “96” that would be within theZone 76 a of FIG. 1-3 wherein the air-fuel mixture would autoignite and,since point “96” is within Zone 76 a of FIG. 1-3, the combustionreaction would occur rapidly, consistent with a short residence time. Asthe combustion process progresses, the temperature of the air-fuel wouldrise while the concentration of combustible gas drops and the processwould follow the arrow from point “96” to point “98.” As point “98” isabove the thermal NOx formation temperature, this process would producea greater quantity of NOx than a process that remains below the thermalNOx formation temperature.

However, if a diluent, such as recirculated flue gas, is added to theair, the oxygen content of the resulting air-diluent mixture is reduced.The use of hot recirculated flue gas can also aid in heating the airfrom point “92” to point “94.” The addition of the diluent to the air,as well as the use of flame stretch mixing technique in mixing fuel intothe air-diluent mixture, moves the upper and lower flammability limitsto new lines annotated as “UFL (air+diluent+stretch)” and “LFL(air+diluent+stretch)” as shown in FIG. 1-4A.

With the addition of a diluent and use of a flame stretch mixingtechnique, point “96” is no longer in Zone 76 a but is in Zone 76 b,where the reaction process would be delayed, longer than in Zone 76 a.The diluents within the mixture reduce the temperature rise so that theprocess follows the arrow from point “96” to point “99” and remainsunder the thermal NOx formation temperature. Thus, use of a diluent canreduce the amount of NOx produced by the combustion/oxidation process.

In certain aspects, a process starting at point 92 heats air to atemperature, indicated by point 82, above an autoignition temperature ofa target air-fuel mixture. Fuel is then injected into the hot air,bringing the sair-fuel mixture to point 97. A reaction chamber, such asreaction chamber 500 of FIG. 1-11, is configured to oxidize the air-fuelmixture and maintain an adiabatic temperature within the reactionchamber above a flameout temperature of the mixture and a maximumreaction temperature within the reaction chamber below the flameouttemperature of the mixture, as indicated by the dashed line connectingpoints 97 and 98 quickly transitioning to below the LFL.

FIG. 1-4B is a diagram 120 of the gradual oxidation process used to heatan external fluid according to certain aspects of the presentdisclosure. Ambient air at point 92 is heated to point 94, wherein fuelis injected into the pre-heated air taking the air-fuel mixture to point96. As the air-fuel mixture is above the auto ignition temperature,gradual oxidation will begin while, at the same time, the air-fuelmixture is transferring heat to an external fluid, for example through asteam coil 5220 of FIG. 5-3, such that the temperature of the air-fuelmixture drops as the fuel concentration also declines to point 122. Theair-fuel mixture then moves away from the external fluid and continuesto gradually oxidize without losing heat to an external fluid such thatthe temperature of the air-fuel mixture rises as the fuel concentrationcontinues to decline, thereby moving to point 124 where the fuel hasbeen completely consumed.

FIG. 1-4C is a diagram 130 of a multi-stage gradual oxidation processaccording to certain aspects of the present disclosure. Anambient-temperature air-fuel mixture at point 132 is heated to point 134that is above the autoignition temperature such that gradual oxidationis initiated and the air-fuel mixture progresses to point 136 whereuponthe fuel is completely consumed. The hot air-diluent mixture is passedthrough a heat exchanger and heat removed, thereby moving theair-diluent mixture to point 138. Additional fuel is injected into theair-diluent mixture, thereby moving the mixture to point 140. Thegradual oxidation process is initiated, as the mixture is still abovethe autoignition temperature, and the process moves along the line topoint 142 whereupon the fuel is again completely consumed. In can beenseen that the hot air-diluent mixture can be again circulated through aheat exchanger as before and the loop of points 142-138-140 repeatedseveral times until all of the oxygen in the mixture is consumed, allthe while keeping the peak reaction temperatures below the thermal NOxformation temperature.

FIGS. 1-5 and 1-6 are flow chart of exemplary gradual oxidationprocesses according to certain aspects of the present disclosure. FIG.1-5 discloses a pre-mix process 100 wherein an oxidant, a diluent, andLEC and HEC fuels are mixed and then heated to an autoignitiontemperature, thereby initiating a gradual oxidation of the fuels. Aparticular embodiment of the process of FIG. 1-5 may include only someof the disclosed steps or may have such steps in an order different fromdepicted in FIG. 1-5. As an example, the most complete process starts atstep 102 wherein an LEC fuel, for example a landfill gas, is provided instep 102.

An oxidant, for example air, is added to the LEC fuel in step 104. Insome aspects, the amount of oxidant added depends on the concentrationof combustible gas in the LEC fuel so as to achieve a targetconcentration of combustible gas in the resulting oxidant-LEC fuelmixture. In some aspects, the amount of oxidant added depends on theconcentration of oxygen in the LEC fuel so as to achieve a minimumconcentration of oxygen in the resulting oxidant-LEC fuel mixture. Insome aspects, the concentration of combustible gas and/or oxygen in theLEC fuel is at least periodically measured and the amount of oxidantbeing added in step 104 adjusted in response to this measurement.

An HEC fuel could optionally be added in step 106. In some aspects, theamount of HEC fuel added depends on the concentration of combustible gasin the oxidant-LEC fuel mixture so as to achieve a target concentrationof combustible gas in the resulting oxidant-LEC-HEC fuel mixture. Insome aspects, the concentration of combustible gas in the oxidant-LECfuel mixture is at least periodically measured and the amount of HECfuel being added in step 106 adjusted in response to this measurement.

Step 108 adds a diluent, such as recirculated flue gas, to theoxidant-fuel mixture. In certain aspects, the amount of diluent isadjusted to achieve a target concentration of combustible gas in theresulting oxidant-fuel-diluent mixture. In certain aspects, therecirculated flue gas also adds heat to the oxidant-fuel mixture,thereby reducing the amount of heat that will be added later in step112. In some aspects, the concentration of combustible gas in theoxidant-fuel mixture is at least periodically measured and the amount ofdiluent being added in step 108 adjusted in response to thismeasurement. The oxidant, LEC and HEC fuels, and diluent are mixed instep 110 into a generally homogeneous mixture. In certain aspects,mixing takes place incrementally after one or more of steps 104, 106,and 108. The homogenous oxidant-fuel-diluent mixture is heated in step112 until the temperature of the mixture reaches at least theautoignition temperature of the mixture. The oxidant-fuel-diluentmixture autoignites in step 114 and gradually oxidizes in step 116 untilthe fuel and oxygen in the mixture no longer react and process 100 isthus completed.

FIG. 1-6 discloses a fuel-injection process 150 wherein an oxidant and adiluent are mixed and then heated to an autoignition temperature,whereupon a mixture of LEC and HEC fuels is injected into theoxidant-diluent mixture and mixed. A particular embodiment of theprocess of FIG. 1-6 may include only some of the disclosed steps or mayhave such steps in an order different from depicted in FIG. 1-6. As anexample, the most complete process starts at step 104 a wherein anoxidant is provided. A diluent is added to the oxidant in step 108 andmixed in step 110 a and heated in step 112 to at least an autoignitiontemperature of a target oxidant-diluent-fuel mixture. In some aspects,the amount of diluent added depends on the concentration of oxygen inthe oxidant so as to achieve a target concentration of oxygen in theresulting oxidant-diluent mixture. In certain aspects, when the diluentis recirculated flue gas, the recirculated flue gas also adds heat tothe oxidant, thereby reducing the amount of heat that will be addedlater in step 112.

In a parallel process, an LEC fuel is proved in step 102 and a HEC fuelis added in step 106 and mixed in step 110 b. In some aspects, theamount of HEC fuel added depends on the concentration of combustible gasin the LEC fuel so as to achieve a target concentration of combustiblegas in the resulting LEC-HEC fuel mixture. In some aspects, theconcentration of combustible gas in the LEC fuel is at leastperiodically measured and the amount of HEC fuel being added in step 106adjusted in response to this measurement.

The LEC-HEC fuel mixture is injected into the hot oxidant-diluentmixture in step 152 and mixed in step 110 c. In certain aspects, themixing of step 110 c comprises providing the oxidant-diluent mixtureinto an oxidation chamber through a turbulence-inducing jet and the fuelmixture is injected into the turbulent oxidant-diluent mixture flow. Theoxidant-diluent mixture and fuel mixture mix rapidly in the turbulentflow in step 110C and then autoignite in step 114 and gradually oxidizein step 116 until the fuel and oxygen in the mixture no longer react andthe process 150 is thus completed.

FIG. 1-7 is a schematic diagram of an exemplary pre-mix oxidation system200 according to certain aspects of the present disclosure. LEC fuel isobtained, in this example, from a landfill 202 through a gas-collectionpiping system 204 and provided as an LEC fuel flow 206 a. In certainaspects, for example if the methane content of the LEC fuel flow 206 ais less than a determined percentage, an HEC fuel 210 is added in amixer 208 a, producing an LEC-HEC fuel mixture 206 b. In certainaspects, for example if the oxygen content of the LEC-HEC fuel mixture206 b is less than a determined percentage, an oxidant 212, for exampleair, is added in a mixer 208 b, producing an oxidant-fuel mixture 206 c.In certain aspects, for example if the oxygen content of theoxidant-fuel mixture 206 c is greater than a determined percentage, adiluent 214, for example recirculated flue gas, is added in a mixer 208c, producing an oxidant-diluent-fuel mixture 206 d. In certain aspects,a mixer 220 is provided to further mix the oxidant-diluent-fuel mixture206 d, thereby producing a homogenized oxidant-diluent-fuel mixture 206e. In certain aspects, a compressor or blower 222 is provided topressurize and heat the homogenized oxidant-diluent-fuel mixture 206 e,thereby producing a pressurized homogenized oxidant-diluent-fuel mixture206 f that is introduced into the oxidizer 224. After the gradualoxidation process is completed, the exhaust 226 exits the oxidizer 224.In certain aspects, a portion of the exhaust 226 is tapped off toprovide the diluent 214. The remaining exhaust 226 is provided to othersystems or vented to atmosphere.

FIG. 1-8 is a schematic diagram of an exemplary injection oxidationsystem 300 according to certain aspects of the present disclosure. Manyelements of system 300 are common to the system 200 previously discussedand their description is not repeated with respect to FIG. 1-8. Insystem 300, the oxidant 212 is compressed and heated separately with acompressor or blower 222 a and the resulting pressurized oxidant 304 isprovided to the oxidizer 224. In certain aspects, a diluent (not shownin FIG. 1-8) is added to the oxidant 212 prior to the compressor 222 a.Separately, the LEC-HEC fuel mixture 206 b is compressed and heated witha separate compressor or blower 222 b to produce a pressurized fuelmixture 302 that is injected into the compressed oxidant-diluent mixture304 within the oxidizer 224. Methods of injecting the fuel mixture 302into the oxidant-diluent mixture 304 within the oxidizer are discussedwith respect to later figures.

FIG. 1-9 is a schematic representation of an exemplary turbine-drivenpower-generation system according to certain aspects of the presentdisclosure. Many elements of system 400 are common to previouslydiscussed systems and their description is not repeated with respect toFIG. 1-9. In system 400, the oxidant-diluent-fuel mixture 206 d isprovided at the inlet of a compressor 410 that is coupled to shaft 412that is also coupled to a turbine 414 and to power generator 416. Thepressurized oxidant-diluent-fuel mixture 206 f from the compressor 410is passed through a heat exchanger 418 wherein the mixture 206 f absorbsheat from the exhaust 420. The heated mixture 206 g is provided to theoxidizer 224. The exhaust 226 is provided to the turbine 414 thatextracts a portion of the energy from the hot compressed exhaust 226,thereby driving the compressor 410 and generator 416 through shaft 412.In certain aspects, a portion of the exhaust from the turbine is tappedoff to provide the diluent 214 and the remaining exhaust 420 passesthrough the previously mentioned heat exchanger 418 and then through asecond heat exchanger 422, wherein the exhaust gas is further cooled bya flow of water 430 before being exhausted to the environment. Theheated water 430, after passing though heat exchanger 422, may be usedfor beneficial uses such as hot water supply, building heating, or otherapplications.

FIG. 1-10 is a schematic representation of another turbine-drivenpower-generation system according to certain aspects of the presentdisclosure. Many elements of system 450 are common to previouslydiscussed systems and their description is not repeated with respect toFIG. 1-10. The system 450 includes a warmer combustor 454 and a turbinecombustor 456 before and after, respectively, the oxidizer 224. An HECfuel 452 is selectively provided to each of the warmer combustor 454 anda turbine combustor 456. The method of using these combustors 454, 456to initiate operation of the oxidizer-driven turbine is described in thepreviously referenced U.S. patent application Ser. No. 13/289,996.

FIG. 1-11 is a cutaway view of an exemplary GO reaction chamber 500according to certain aspects of the present disclosure. The GO reactionchamber 500 has a vessel 510 that, in certain aspects, is configured towithstand a pressurized internal gas. A tower 514 is positioned, in thisexample, along a center axis of the vessel 510, and configured to acceptat an external end a flow of an oxidant-diluent-fuel mixture 530 throughinlet 515. A plurality of distribution pipes 516 are coupled to thetower 514 such that the oxidant-diluent-fuel mixture 530 passes from thetower into the distribution pipes 516. Each of the distribution pipes516 comprise a plurality of injection holes (not visible in FIG. 1-11)that allow the mixture 530 to pass from the interior of the distributionpipes 516 into the interior of the vessel 510. The interior of thevessel is at least partially filled with a porous media 512. This media512 absorbs heat from the GO process and then releases this heat tounreacted mixture 530, thereby raising the temperature of the unreactedmixture 530 above the autoignition temperature. Porous media 512 alsofunctions to mix products of oxidation from prior stages with unreactedoxidant-diluent-fuel mixtures injected through pipes 516.

In certain aspects, the GO reaction chamber 500 comprises one or moresecondary inlets 518 through which an oxidant, a fuel, or a mixturethereof can be injected directly into the interior of the vessel 510. Incertain aspects, the GO reaction chamber 500 comprises one or moreheaters 522 that may be used to heat the porous media 512. In certainaspects, the GO reaction chamber 500 comprises one or more sensors 524that are configured to measure one or more of a temperature, an oxygencontent, or a fuel content of the gases at one or more points within thevessel 510.

In certain aspects, the GO reaction chamber 500 comprises a sensor 524that comprises a temperature sensing element and outputs a signal thatis representative of a temperature within the reaction chamber 500. Incertain aspects, the GO reaction chamber 500 comprises a sensor 525 thatcomprises a temperature sensing element and outputs a signal that isrepresentative of the temperature of the oxidant-diluent-fuel mixture530. In certain embodiments, the temperature signals from sensors 524and 525 are accepted by a controller 529 that outputs a signal 532 toreduce the temperature within the reaction chamber 500 when thetemperature within the reaction chamber 500 approaches a flameouttemperature, such that the temperature remains beneath the flameouttemperature. In certain embodiments, adjustment of the temperaturewithin the reaction chamber 500 is accomplished by adjusting one or moreof the flow of the oxidant-diluent-fuel mixture 530, the composition ofthe oxidant-diluent-fuel mixture 530, the temperature of theoxidant-diluent-fuel mixture 530, the flow of the auxiliary air-fuelmixture 540, the composition of the auxiliary air-fuel mixture 540, thetemperature of the auxiliary air-fuel mixture 540, the flow of exhaustgas through outlet 520, a flow of a coolant through an internal heatexchanger such as shown in FIG. 2-3 (not shown in FIG. 1-11), or a flowof a non-combustible fluid introduced into the reaction chamber 500through an injection subsystem (not shown in FIG. 1-11). In certainaspects, the signal 532 is provided to a control module 531 configuredto control at least one of a flow rate, a composition, and a temperatureof the oxidant-diluent-fuel mixture 530.

In certain aspects, the detection module 527 is configured to detectwhen at least one of a reaction temperature within the reaction chamber500, for example the temperature at sensor 524, approaches or exceeds aflameout temperature of the oxidant-diluent-fuel mixture within thereaction chamber 500 and a reaction chamber inlet temperature, i.e. thetemperature of the oxidant-diluent-fuel mixture 530 at sensor 525,approaches or drops below an autoignition threshold.

In certain aspects, the controller 529 comprises a correction module 528that outputs instructions, based on the detection module 527, to changeat least one of removal of heat from the reaction chamber and thetemperature of the oxidant-diluent-fuel mixture 530 at the inlet of thetower 514 within the reaction chamber 500. In certain aspects, thecorrection module 528 is configured to maintain an actual temperaturewithin the reaction temperature, for example at sensor 524, to atemperature below the flameout temperature and/or maintain the inlettemperature above the autoignition threshold of the fuel. In certainaspects, the controller 529 is configured to maintain the temperature ofthe oxidant-diluent-fuel mixture 530 at the inlet to tower 514 above theautoignition threshold, such that the gas within the reaction chamber500 oxidizes without a catalyst. In certain aspects, the controller 529is configured to determine at least one of a reduction of thetemperature within the reaction chamber to remain below the flameouttemperature, and an increase in the temperature of theoxidant-diluent-fuel mixture 530 at the inlet to tower 514 to maintainthe temperature of the oxidant-diluent-fuel mixture 530 above theautoignition threshold.

In certain aspects, the controller 529 is configured such that when thetemperature of the oxidant-diluent-fuel mixture 530 at the inlet totower 514 approaches or drops below an autoignition threshold of theoxidant-diluent-fuel mixture 530, the controller 529 outputs a signal532 to cause additional heat to be added to the oxidant-diluent-fuelmixture 530 such that the temperature of the oxidant-diluent-fuelmixture 530 at the inlet to tower 514 is maintained above theautoignition threshold, and the reaction chamber 500 maintains oxidationof the fuel within the reaction chamber 500 without a catalyst. Incertain embodiments, the correction module 528 outputs instructions,based on the detection module 527, to change either a residence time ofthe gas within the reaction chamber, for example by reducing the flow ofthe oxidant-diluent-fuel mixture 530, and/or changing the autoignitiondelay time, for example by adjusting the composition of theoxidant-diluent-fuel mixture 530 or increasing the temperature withinthe reaction chamber 500 with the heater 522, within the reactionchamber sufficient for the oxidant-diluent-fuel mixture 530 toautoignite and oxidize while within the reaction chamber 500.

In certain aspects, the detection module 527 is configured to detectwhen a reaction chamber inlet temperature of the gas approaches or dropsbelow a level such that the reaction chamber alone will not supportoxidation of the fuel, and the correction module 528 is configured tochange, based on the detection module 527, the residence time of the gaswithin the reaction chamber and/or the autoignition delay time withinthe reaction chamber sufficient for the gas to autoignite and oxidizewhile within the reaction chamber 500.

In some embodiments, the temperature of the fuel or gas mixture withinthe reaction chamber may be above the lower flammability limit or theflameout temperature. In these instances, for example, mixing a HEC fuelgas into the reaction chamber, there may be a period of time that themixture passes through a flammability area, which is below the upperflammability limit and above the lower flammability limit. While aresidence time within this area may not be, in some instances,desirable, the residence time of the mixture within the area can bereduced by either changing the temperature of the mixture or changingthe flow of the mixture. In some instances, heat may be drawn out of thereaction chamber to reduce the temperature of the mixture to be belowthe lower flammability limit, or flameout temperature, such that theresidence time of the mixture within the flammability area is less thanthe autoignition delay time. In some instances, the flow rate of themixture through the reaction chamber can be increased to reduce theresidence time of the mixture within the reaction chamber; this reducedresidence time of the mixture within the reaction chamber can equate toa reduced residence time of the mixture being exposed to temperatureswithin the reaction chamber that are within the flammability area andmay be acceptable if the residence time is less than the autoignitiondelay time. In some instances, heat may be added to the mixture suchthat the reaction temporarily moves into a flammability area for a briefperiod of time relative to the autoignition delay time.

In some instances, at least one of the temperature or the flow of themixture through the reaction chamber can be controlled such that theresidence time of the fuel within the flammability area is less than 5%of the autoignition delay time. In some instances, the residence time ofthe fuel within the flammability area can be between about 5% and about10% of the autoignition delay time. In some instances, the residencetime of the fuel within the flammability area can be between about 10%and about 20% of the autoignition delay time. In some instances, theresidence time of the fuel within the flammability area can be betweenabout 15% and about 25% of the autoignition delay time. In someinstances, the residence time of the fuel within the flammability areacan be between about 25% and about 50% of the autoignition delay time.In some instances, the residence time of the fuel within theflammability area can be between about 30% and about 75% of theautoignition delay time.

In certain aspects, the control module 531 is configured to raise thetemperature of the oxidant-diluent-fuel mixture 530 at or before theinlet 515 to or above an autoignition temperature of theoxidant-diluent-fuel mixture 530. In certain embodiments, the reactionchamber 500 is configured to oxidize the oxidant-diluent-fuel mixture530 and maintain an adiabatic temperature above the autoignitiontemperature of the oxidant-diluent-fuel mixture 530 and a maximum actualtemperature of the reaction chamber 500 below a flameout temperature ofthe oxidant-diluent-fuel mixture 530.

In certain aspects, the oxidizer 500 is configured to create theoxidant-diluent-fuel mixture 530 by mixing, in a system not shown inFIG. 1-11, a gas having a LEC fuel with one or more of the group of agas comprising a HEC fuel, a gas comprising an oxidant, and a gascomprising a diluent while all of the gases are at temperatures belowthe autoignition temperature of any of the gases being mixed. Theoxidizer 500 is also configured to increase the temperature of theoxidant-diluent-fuel mixture 530 to at the least an autoignitiontemperature of the oxidant-diluent-fuel mixture 530 and allowing theoxidant-diluent-fuel mixture 530 to autoignite, and then maintaining thetemperature of the oxidant-diluent-fuel mixture 530 below a flameouttemperature while the autoignited the oxidant-diluent-fuel mixture 530oxidizes.

In certain aspects, the porous media 512 within the oxidizer 500 isconfigured to maintain an internal temperature of the reaction chamberbelow a flameout temperature and to maintain a reaction chamber inlettemperature of the fuel to be greater than an autoignition temperatureof the fuel. In certain aspects, at least one flow path from the inletto the outlet of the oxidizer 500 is configured to direct theoxidant-diluent-fuel mixture 530 through a portion of the porous media512 that is hotter than the autoignition temperature of theoxidant-diluent-fuel mixture 530 until the oxidant-diluent-fuel mixture530 reaches a temperature above the autoignition temperature of theoxidant-diluent-fuel mixture 530, whereupon the flow path is furtherconfigured to direct the oxidizing oxidant-diluent-fuel mixture 530 tothe outlet along a path being generally opposite to the first flow path,for example using internal baffles such as the tubes 1055/1060 shown inFIG. 2-7B.

In some embodiments, the controller 529 can direct other parts of theoxidation system. For example, other controls that the controller 529may direct are described in copending U.S. patent application Ser. Nos.13/289,989, filed Nov. 4, 2011, and 13/289,996, filed Nov. 4, 2011, bothof which are incorporated by reference herein in their entirety to theextent the teachings within the applications are not inconsistent withthe teachings of this description.

FIG. 1-12 schematically depicts the flow through a gradual oxidationsystem 4500 having a sparger according to certain aspects of the presentdisclosure. The processes and elements of FIG. 1-12 are described inrelation to the oxidizer 500 of FIG. 1-11. The following processes occuras air 4502 and fuel 4220 flow through the oxidizer:

-   -   1. Fuel/air mixer 4510 creates an initial lean air-fuel mixture        from one or both of air 4502 and fuel 4220.    -   2. Heater 4512 heats the air-fuel mixture up to temperatures        proximate to the autoignition temperature. The heat may also be        added through compression of the mixture as well as heat        exchange. In some embodiments, heat may be added by introducing        a heated gas (e.g., flue gas).    -   3. A first stage gradual oxidizer that may include a heater 522        (FIG. 1-11) or heater 4516 (FIG. 1-12), for example a pilot        burner, to initiate the gradual oxidation 4518. In certain        aspects, this heater is an electric heater of various types        known to those of skill in the art. The output of this is hot        gas comprising un-consumed 0₂ and oxidation products C0₂ and        H₂0, Since the portion of fuel and air flowing into this first        oxidizer 4518 is small, less heat is required to heat the        mixture above the autoignition temperature to initiate the        oxidative reaction. In certain aspects, heat is added to the        first stage by preheating a porous media with a        starter-combustor upstream. The preheated media then heats the        fuel/air mixture in 4516 to start the oxidation. Since only a        small portion of flow goes through the heated media in heater        4516, thermal condition and radiation of energy opposite the        flow direction is able to maintain the media temperature high        enough to continue to heat the flow. This stage anchors the        reaction.    -   4. A divide-mix-oxidize stage 4530, for example as occurs in an        arm 516 of sparger 514 of FIG. 1-11, wherein a portion of the        air-fuel mixture is split off, mixed with the hot gas from the        prior process, and gradually oxidized, shown as processes 4514,        4520, and 4518. Since the prior oxidized gases from oxidizer        4518 are hot, typically above 1400° F. but below 2300° F., they        serve to heat the unreacted fuel and air from divider 4514 in        mixer 4520, and initiate the oxidation of this next stage of        oxidation    -   5. A repetition of stage 4530 oxidizes all of the fuel from LEC        source 4220 so that no fuel remains after the final oxidizer        4518. The staged-approach to starting the oxidation process in        the anchoring first stage, and the oxidizing portions of the gas        thereafter, is the gradual oxidation process.

FIG. 1-13 is a schematic representation of a multi-stage GO reactionchamber 600 according to certain aspects of the present disclosure. Inthis example, the chamber 600 comprises four reaction chambers 602 a,602 b, 602 c, and 602 d that are serially coupled together. In thisexample, a flow of an air-fuel mixture 604, for example an LEC fuel, isprovided into each of the four reaction chambers 602 a, 602 b, 602 c,and 602 d. In certain aspects, the amount of the air-fuel mixture 604provided into each reaction chamber 602 a, 602 b, 602 c, and 602 d isdifferent. In certain aspects, one or more different air-fuel mixtures(not shown in FIG. 1-12) are provided to the downstream reactionchambers 602 b, 602 c, and 602 d. In certain aspects, an oxidant (notshown in FIG. 1-13) is separately provided to one or more of thedownstream reaction chambers 602 b, 602 c, and 602 d. In certainaspects, an HEC fuel (not shown in FIG. 1-13) is separately provided toone or more of the reaction chambers 602 a, 602 b, 602 c, and 602 d.

FIG. 1-14 is a schematic representation of a fluidized bed GO reactionchamber 700 according to certain aspects of the present disclosure. Inthis example, the reaction chamber 700 comprises a vessel 710 at leastpartially filled with a media 720 that, when a gas is introduced at thebottom of the media 720, becomes fluidized. The air-fuel-diluent mixture604 gradually oxidizes as the mixture 604 passes through the fluidizedmedia 720 and is removed at the top as exhaust 226. The fluidized mediacirculates within vessel 710, transferring heat from the exhaustproducts of oxidation to the inlet reactants. Fluidized particles 720near the exhaust end of vessel 710 (proximal to exhaust 226) are heatedby hot products of oxidation. The fluidized media then is conveyed,either purposely or incidentally, to the inlet end of the oxidationvessel 710. The heated fluidized media then impart their heat to theincoming, cooler, unreacted air-fuel-diluent mixture 604 to heat theflow, as is taught for the GO process. Fluidized media 720 thereforeserves to transfer the heat from the products of oxidation to theair-fuel-diluent reactants. There are many ways to implement fluidizedbeds to move heat around closed chemically reacting systems, especiallywhen combined with the staged-injection of the GO process, andimplementing fluidized beds is one example of how heating isaccomplished (see, e.g., FIG. 1-12, 4512, 4516).

FIG. 1-15A is a schematic representation of a recirculating bed GOreaction chamber 800 according to certain aspects of the presentdisclosure. In this example, the reaction chamber 800 comprises a vessel810 that is at least partially filled with a media 820. A portion 810 aof the media 820 is at least periodically removed at the bottom of thevessel 810 and transported through a transfer system 820 to the top ofvessel 810, whereupon the portion 810 a is returned to the interior ofvessel 810. At the same time, a flow of an air-fuel mixture 604 isintroduced at the bottom of the vessel 810 and passes upward through themedia 820. The mixture 604 gradually oxidizes as it passes through themedia 820 and is removed at the top as exhaust 226. As the media 820that is within the vessel 810 is moving downward as portions 810 a areremoved at the bottom, the hottest media 820, i.e. the media 820 that ison top of the media 820 that is within the vessel 810, moves toward theinlet thereby counteracting the tendency of the incoming air-fuelmixture 604 to locally cool the media 820. The cold media portions 810 aremoved from the bottom are delivered to the top where the portions 810a are heated by the hot oxidized gas.

FIG. 1-15B is a schematic representation of another recirculating bed GOreaction chamber 801 according to certain aspects of the presentdisclosure. In this embodiment, the recirculating portions 810 b aredrawn from a hot portion of the bed 820, for example a midpoint in thedepth of the bed 820, and circulated through pipe 822 wherein heat 824is extracted from the recirculating portions 810 b. The cooled portions810 b are provided back to the chamber 801, for example at the top so asto fall onto the top of the bed 820. This extraction of heat from therecirculating portions 810 b draws heat from the reaction chamber 801.In certain aspects, the flow rate of portions 810 b is controlled tomaintain an internal temperature of the reaction chamber 801 below aflameout temperature.

FIG. 1-16 is a schematic representation of a GO reaction chamber 850with flue gas recirculation according to certain aspects of the presentdisclosure. The vessel 810 and media 820 are similar to those of the GOoxidizer 800 of FIG. 1-15. In the example of FIG. 1-16, however, aportion 852 of the exhaust gas 226, also referred to herein as flue gas,is recirculated and provided at the bottom of the vessel 810 so as toheat the incoming air-fuel mixture 604 and anchor the GO process withinthe vessel 810, as well as provide an additional diluent to the incomingair-fuel mix 604.

In certain aspects, the GO reaction chamber 850 comprises an oxygensensor, such as sensor 524 of FIG. 1-11, that is configured to determinean oxygen content level within the reaction chamber 850 and provide asignal representative of the oxygen content level. In certain aspects, acontroller (not shown in FIG. 1-16) accepts the oxygen content levelsignal and outputs instructions to introduce flue gas 852, received fromthe outlet of the reaction chamber and containing product gases fromoxidation of the fuel within the reaction chamber, into the reactionchamber 850 based on the oxygen content level.

In certain embodiments, an oxidizer can includes a reaction chamberinlet configured to accept a gas having a mixture of alow-energy-content (LEC) fuel and at least one of the group of ahigh-energy-content (HEC) fuel, an oxidant-comprising (OC) gas, and adiluent-containing (DC) gas. The gas mixture can be regulated to be at atemperature below an auto-ignition temperature of the gas mixture. Theoxidizer can also include a heat exchange media disposed within thereaction chamber. The media may be configured to maintain an internaltemperature of the reaction chamber below a flameout temperature and tomaintain a reaction chamber inlet temperature of the fuel to be greaterthan an autoignition temperature of the fuel. The reaction chamber canprovide at least one flow path through the chamber from the inlet to theoutlet. The flow path may be configured to direct the gas entering theinlet through a first path through media that is hotter than anauto-ignition temperature of the gas mixture until the gas mixturereaches a temperature above the auto-ignition temperature of the gasmixture, whereupon the flow path is further configured to direct theoxidizing gas mixture through a second path through the media to theoutlet, the second path being generally opposite to the first flow path.Examples of this are illustrated in FIGS. 2-7A through 2-9.

In certain embodiments, a method of oxidization described hereinincludes the steps of receiving into a reaction chamber, via a chamberinlet, the inlet configured to accept a gas having a mixture of alow-energy-content (LEC) fuel and at least one of the group of ahigh-energy-content (HEC) fuel, an oxidant-comprising (OC) gas, and adiluent-containing (DC) gas, the gas mixture being at a temperaturebelow an auto-ignition temperature of the gas mixture; maintaining aninternal temperature of the reaction chamber below a flameouttemperature by heat exchange media disposed within the reaction chamber,maintaining a reaction chamber inlet temperature of the fuel to begreater than an autoignition temperature of the fuel by transferringheat through the heat exchange media, and directing gas entering theinlet through a first path through media that is hotter than anauto-ignition temperature of the gas mixture until the gas mixturereaches a temperature above the auto-ignition temperature of the gasmixture; and directing the gas through a second path through the mediato a chamber outlet, the second path being generally opposite to thefirst flow path.

In certain embodiments, the reaction chamber is configured to maintainoxidation of the gas mixture along at least one of the first and secondflow paths without a catalyst. In certain embodiments, the reactionchamber is configured to maintain oxidation of the mixture beneath theflameout temperature of the gas mixture by circulating heat exchangemedia outside the reaction chamber. In certain embodiments, the systemalso includes at least one of a turbine or a piston engine that isconfigured to receive gas from the reaction chamber outlet and expandthe gas. In certain embodiments, the gas mixture comprises at least oneof hydrogen, methane, ethane, ethylene, natural gas, propane, propylene,propadiene, n-butane, iso-butane, butylene-1, butadiene, iso-pentane,n-pentane, acetylene, hexane, and carbon monoxide.

In certain embodiments, the oxidizer described can include a reactionchamber inlet that is configured to accept a gas having a mixture of alow-energy-content (LEC) fuel and at least one of the group of ahigh-energy-content (HEC) fuel, an oxidant-comprising (OC) gas, and adiluent-containing (DC) gas. The gas mixture can be regulated to be at atemperature below an auto-ignition temperature of the gas mixture. Theoxidizer can also have a heat controller that is configured to increasea temperature of the gas mixture to at the least an autoignitiontemperature of the gas mixture, thereby permitting the gas mixture toautoignite and to maintain the temperature of the gas mixture below aflameout temperature while the autoignited gas mixture oxidizes.

In some methods of oxidizing a fuel described herein includes the stepsof mixing a gas having a low-energy-content (LEC) fuel with one or moreof the group of a gas comprising a high-energy-content (HEC) fuel, a gascomprising an oxidant, and a gas comprising a diluent to form a gasmixture, wherein all of the gases are at temperatures below theautoignition temperature of any of the gases being mixed; increasing thetemperature of the gas mixture to at the least an autoignitiontemperature of the gas mixture and allowing the gas mixture toautoignite; and maintaining the temperature of the gas mixture below aflameout temperature while the autoignited gas mixture oxidizes.

In certain embodiments, the oxidizer can include an inlet configured toaccept a gas having a mixture of a low-energy-content (LEC) fuel and atleast one of the group of a high-energy-content (HEC) fuel, anoxidant-comprising (OC) gas, and a diluent-containing (DC) gas. The gasmixture can be regulated to be at a temperature below an auto-ignitiontemperature of the gas mixture. A controller (e.g., a heat controller)can be configured to heat the gas to at the least an auto-ignitiontemperature of a first gas mixture, comprising a gas with an oxidantmixed with determined ranges of a low-energy-content (LEC) fuel and ahigh-energy-content (HEC) fuel. An inlet (e.g., an injector) can also beconfigured to inject, after the first gas is heated to at the least anauto-ignition temperature of a first gas mixture, a second gas mixtureof the LEC fuel gas and the HEC fuel. The inlet or injector can injectsa ratio of the LEC and HEC gas and at a rate of injection that isselected to produce substantially the same ratio of LEC and HEC gas asthe first gas mixture when the gas is injected into the reactionchamber. The reaction chamber can be configured to mix the injectedsecond gas with the heated gas containing an oxidant at a rate toproduce a substantially homogeneous first gas mixture in a time lessthan the ignition delay time for the second gas mixture and allowing thefirst gas mixture to auto-ignite and to maintain the temperature of thefirst gas mixture below a flameout temperature while the auto-ignitedfirst gas mixture oxidizes.

In certain embodiments, a method of oxidation described herein includesthe steps of heating a gas comprising an oxidant to at the least anauto-ignition temperature of a first gas mixture comprising a gas withan oxidant mixed with determined ranges of a low-energy-content (LEC)fuel and a high-energy-content (HEC) fuel; injecting, after the heating,a second gas mixture of the LEC fuel gas and the HEC fuel, wherein theratio of the LEC and HEC gas and the rate of injection are selected toproduce substantially the same first gas mixture ratios when injectedinto the heated gas containing an oxidant; mixing the injected secondgas with the heated gas containing an oxidant at a rate to produce asubstantially homogeneous first gas mixture in a time less than theignition delay time for the second gas mixture and allowing the firstgas mixture to auto-ignite; and maintaining the temperature of the firstgas mixture below a flameout temperature while the auto-ignited firstgas mixture oxidizes.

FIGS. 1-17A and 17B depict a GO reaction chamber 860 with structuredreaction elements 864 according to certain aspects of the presentdisclosure. FIG. 1-17A is a schematic representation of a vessel 862that contains, in this example, a stack of structured reaction elements864.

FIG. 1-17B shows an exemplary structured reaction element 864 that isformed as a disk 866 with a plurality of holes 868 through the thicknessof the disk 866. In certain embodiments, the edges of the disk 866 areraised so as to provide a gap between stacked elements 864 therebyallowing lateral flow of the air-fuel mixture between holes as theair-fuel mixture passes through a stack of the reaction elements 864.When stacked in the vessel 862, the elements 864 may be randomly rotatedabout a center point so that the holes 868 of adjacent elements 864 donot line up, thereby providing a more serpentine path through a stack ofelements 864.

As another example of the structured media inside vessel 862 (FIG.1-17A), extruded metal or ceramic such as cordierite will serve toconduct heat from downstream of the flow, near exit 226, to upstream ofthe flow. This will serve to heat the inlet air-fuel mixture 604 abovethe autoignition temperature and initiate the oxidation reactions.

Gradual Oxidizer as Heat Source

FIG. 2-1 is a schematic representation of an oxidizer 224 coupled to aheat exchanger 1010 to provide process heating to an industrial processaccording to certain aspects of the present disclosure. In FIG. 2-1, thegradual oxidation reactant gases 604 are admitted into the oxidizer 224and undergo gradual oxidation and leave as product gases 1015 that passthrough a heat exchanger 1010 wherein heat is rejected and the productgases are exhausted to the atmosphere as exhaust 1030 at a reducedtemperature. Entering the other passage of the heat exchanger 1010 is acool fluid 1020, for example air, water, or an industrial fluid, whichis beneficially heated and exits as hot fluid 1025 that flows to itspoint of use (not shown in FIG. 2-1). Heat exchanger 1010 can beconfigured as co-flow, counterflow, cross-flow, or any of the other heatexchanger options described and illustrated herein or other that may beknown in the art. The gradual oxidation reaction products 1015, whichare comprised of pollutant-free hot gases, are directed to a heatexchanger that beneficially heats a stream of air to warm a living spacefor personal comfort, or a volume of water for domestic usage, or anyindustrial material requiring heating.

FIG. 2-2 is a schematic representation of an oxidizer 224 coupled to aheating chamber 1050 to heat a process material 1055 according tocertain aspects of the present disclosure. The air-fuel mixture 604 isadmitted into the oxidizer 224 where it undergoes gradual oxidation andleaves as product gas 1015, after which it proceeds into the heatingchamber 1050 where a material 1055 is beneficially heated by the hotgases, after which the gases exit the heating chamber as exhaust 1030and are exhausted to atmosphere. The material 1055 may be processed byone or more of thawing, melting, evaporating, subliming, drying, baking,curing, sintering, or calcining using the beneficial heat. In a similarembodiment (not shown in FIG. 2-2), where ventilation is sufficient toprevent harmful levels of oxygen depletion, the hot gradual oxidationreaction products are directed into an occupied space for comfortheating. In another similar embodiment (not shown in FIG. 2-2), the hotproducts are directed to an absorption chiller to provide the motiveenergy for an absorption-refrigeration cycle.

FIG. 2-3 is a schematic representation of an oxidizer 224 comprising aninternal heat exchanger 1060 through which a fluid passes according tocertain aspects of the present disclosure. The heat exchanger 1060 isdisposed internally to the oxidizer 224 reaction chamber. The air-fuelmixture 604 is admitted into the oxidizer 224 and undergoes gradualoxidation. Cool fluid 1020 enters the heat exchanger 1060 and a portionof the thermal energy generated by the gradual oxidation process istransferred to the fluid through the heat exchanger 1060. The cooledproduct gasses exit as exhaust 1030. The hot fluid 1025 exits the heatexchanger 1060 and is directed to its point of use (not shown in FIG.2-3). An example embodiment of the oxidizer 224 comprises a vessel linedinternally with tubes where air is conveyed through the tubes.

In certain embodiments, heat is drawn from the reaction chamber of theoxidizer 224 using one of the cool fluid 1020 being a liquid that atleast partially vaporizes in the heat exchanger 1060, the cool fluid1020 being a gas, or the cool fluid 1020 being a liquid that increasesin temperature without vaporizing. In certain embodiments, the amount ofheat being drawn from the reaction chamber of oxidizer 224 is adjustedby one or more of controlling the flow rate of the cool fluid 1020,controlling the flow rate of the hot fluid 1025, or controlling thetemperature of at least one of the cool fluid 1020 and the hot fluid1025. In certain aspects, the cool fluid 1020 is at a temperature thatis less than an internal temperature within the oxidizer 224, whereinthe reaction chamber is configured to maintain the internal temperatureabove an autoignition temperature of the fuel within the air-fuelmixture 604 and below a flameout temperature of the fuel within theair-fuel mixture 604.

FIG. 2-4 is a schematic representation of another embodiment of anoxidizer 224, comprising a plurality of internal heat exchangers 1060according to certain aspects of the present disclosure. Similar to FIG.2-3, an air-fuel mixture 604 is admitted into an oxidizer 224 wheregradual oxidation occurs and a portion of the thermal energy istransferred to a cool fluid 1020 through the heat exchangers 1070, whichare disposed internally to the gradual oxidizer 224. In certainembodiments, the heat exchangers 1060 comprise a plurality of the heatremoval surfaces (not shown in FIG. 2-4) that are positioned internallyproximate to the outer circumference of the oxidizer vessel to absorbmuch of the beneficial heat that might otherwise be lost to theenvironment through imperfect wall insulation.

FIG. 2-5 is a schematic representation of an oxidizer 224 comprising aplurality of gradual oxidation zones 1075A-1075C with adjoining reactionzones 1080A-1080C wherein batches of a process material are heatedaccording to certain aspects of the present disclosure. An air-fuelmixture 604 is admitted into an oxidizer 224 in three separate reactantstreams 1090A, 1090B, and 1090C that are respectively directed togradual oxidation zones 1075A-1075C where gradual oxidation and therelease of exothermic energy from the gases occur. Granular, industrialmaterials (not visible in FIG. 2-5) are disposed within the reactionzones 1080A-1080C where they are fluidized by the reactant gases and arebeneficially heated in a batch manner. A fraction of the heat removalsurface is positioned in such a manner that it absorbs sufficientbeneficial heat from the gradual oxidation process to reduce localtemperatures below the point where damage to internal components mayoccur. The product gases from the gradual oxidation process arerecombined into a single exhaust stream 1030 that exits to atmosphere orother end use. In a similar embodiment (not shown in FIG. 2-5),additional heat removal surfaces are provided so as to permit thegradual oxidation process to be operated at greaterenergy-release-density (and thereby, smaller overall reactor volume)without overheating and damaging internal components.

FIG. 2-6 is a schematic representation of an oxidizer 224 comprising aplurality of gradual oxidation zones 1075A-1075C with adjoining reactionzones 1120A-1120C wherein continuous flows of a process material 1105are heated according to certain aspects of the present disclosure. As inFIG. 2-5, an air-fuel mixture 604 is admitted into an oxidizer 224 inthree separate reactant streams 1090A, 1090B, and 1090C that arerespectively directed to gradual oxidation zones 1075A-1075C wheregradual oxidation and the release of exothermic energy from the gasesoccurs, followed by recombination of the product gas streams into asingle exhaust 1030 that exits to atmosphere. Cold, unreacted, granular,industrial materials 1105A-1105C are admitted into reaction zones1120A-1120C where the materials are fluidized by the gradual oxidationreactant gases and are heated in a continuous manner to abeneficially-altered condition 1110A-1110C that is removed from theoxidizer 224.

On the downstream side of the each reaction zone 1120A-1120C are weirs1085A-1085C that retain a portion of the beneficially heated granularmaterials and permit the balance 1110A-1110C to exit the oxidizer 224whereupon the altered materials are collected for later use (not shownin FIG. 2-6). Each of the multiple stages of a gradual oxidation processare independently carried out in the presence of a circulating fluidizedbed of granular process material, which concurrently exchanges heat withthe reacting gradual oxidation gases while the material 1105A-1105Citself undergoes a drying, curing, sintering, calcining, or otherthermally-induced alteration due to the heat from the gradual oxidationgases. The circulating fluidized bed process that beneficially altersthe granular material can be performed in a batch or continuous mannerin each gradual oxidation stage. In a continuous process, the additionrate of cold, unreacted granular material 1105A-1105C should besufficiently small to ensure the gradual oxidation process is notquenched and extinguished. In certain embodiments, the mass rate of coldunreacted granular material 1105A-1105C being continuously added to thereaction zones 1120A-1120C is 1-20% of the mass flow rate of gradualoxidation gases entering the reaction zones 1120A-1120C.

FIGS. 2-7A and 2-7B are a perspective view and cross-section view of anexample design detail of an oxidizer element 1150 according to certainaspects of the present disclosure. Two concentric pipes 1055 and 1060are used to form a process flow path wherein the incoming air-fuelmixture 604 enters the inner pipe 1060 at point A flows through thesmaller pipe 1060, and then exits the inner pipe 1060 at point B andcounter-flows between the inner pipe 1060 and the outer pipe 1055 whilecontinuing to gradually oxidize and then exits the oxidizer element 1150at point C as fully oxidized product gas. As the air-fuel mixture 604flows through the inner pipe 1060, the mixture is heated through wallsof pipe 1060 by the hot product gas counter-flowing past the outside ofthe pipe 1060.

FIG. 2-8 is a plot of the temperatures within the oxidizer of FIGS. 2-7Aand 2-7B according to certain aspects of the present disclosure.Incoming air-fuel mix at point A is at temperature T₁. The mixture isheated during the initial part of the flow through inner pipe 1060 byheat transfer from the hot gas counter-flowing between the inner pipe1060 and the outer pipe 1055 to the temperature T₂ when the gradualoxidation reaction is initiated. Exothermal release of chemical energyin the gradual oxidation process raises the temperature to T₃ when themajority of the reaction has already occurred. Gas then enters themiddle section between the two concentric pipes 1055 and 1060 and flowsback counter to the initial flow. The gas temperature may continue toincrease slightly, due to continued gradual oxidation, or decrease asheat is lost to the outer pipe 1055. The gas then keeps moving andexchanges thermal energy with the incoming (colder) air-fuel mix 604through the walls of the inner pipe 1060, thereby cooling the productgas to T₄.

FIG. 2-9 is a cross-sectional view of an assembly using the oxidizerelement of FIGS. 2-7A and 2-7B according to certain aspects of thepresent disclosure. The assembly 1200 comprises multiple elements 1150disposed in a housing 1205 that, in this example, is a cylindricalvessel. In certain embodiments, the vessel 1205 is a shape other thanround. In certain embodiments, the vessel 1205 is pressurized. Two solidcross-sectional plates 1210 and 1220 are positioned across the interiorof vessel 1205. The inner pipes 1160 penetrate the plate 1210 and theouter pipes 1055 are attached to plate 1220. Separate passages 1225 areprovided through the plate 1220. An air-fuel mixture 604 flowing throughthe vessels 1205 passes into each of the inner pipes 1060, through thepipes 1060 and 1055 as previously discussed with respect to FIGS. 2-7Aand 2-7B, and then past the outside of outer pipes 1055 and through thepassages 1225. As the air-fuel mixture 604 is converted into a productgas, the mixture travels three times through the same length of thevessel 1205: (1) through the inner pipes 1060, (2) between the inner andouter pipes 1060 and 1055, and (3) through the volume between outside ofthe outer pipes 1055 and the vessel 1205. This provides additional heatexchange and promotes higher efficiency and a smaller volume of theoxidizer assembly 1200.

Schnepel Cycle for Reciprocating Engine

FIG. 3-1 is a schematic of an exemplary Schnepel cycle power generationsystem 3000 according to certain aspects of the present disclosure. Anair-fuel mixture 3005, comprising a mixture of an LEC fuel, HEC fuel,oxidant, and diluent as described with reference to the air-fuel mixture206 e of FIG. 1-7, is provided to a compressor cylinder 3010 having apiston 3030 a that is coupled through a connecting rod 3032 to acrankshaft 3034 that is generally similar to the crankshafts found inconventional internal-combustion engines having reciprocating cylinders.In certain aspects, the compressor cylinder 3010 is a part of a driveassembly 3036 as indicated by the dashed line box 3036 that, as anassembly, is generally similar to portions of conventionalinternal-combustion engines having reciprocating cylinders. As thepiston 3030 a descends within the compressor cylinder 3010, the air-fuelmixture 3005 is drawn into the internal space 3015 through acontrollable intake valve (not shown in FIG. 3-1). When the piston 3030a is near the bottom of its stroke, the intake valve closes. As thepiston 3030 a ascends, the internal volume 3015 is reduced, therebycompressing the air-fuel mixture 3005. When the piston 3030 a reaches adesignated point, an outlet valve (not shown in FIG. 3-1) opens andconnects the internal space 3015 to line 3040, thereby allowing thecompressed air-fuel mixture 3005 to flow into line 3040. In thisexample, the compresses air-fuel mixture 3005 passes through arecuperator 3045 and then through line 3050 into a heat exchanger 3055,then into line 3060 and into the oxidizer 224.

As previously described, the air-fuel mixture 3005 is gradually oxidizedwithin the oxidizer 224 and exists as a hot combustion product gas inline 3065. This hot gas is routed to the second side of the heatexchanger 3055, wherein the hot gas transfers a portion of its thermalenergy to the incoming air-fuel mixture 3050. The product gas now flowsthrough line 3070 into the internal space 3025 of an expander cylinder3020.

In operation, an inlet valve (not shown in FIG. 3-1) opens when thepiston 3030 b is at or just past top-dead-center such that the hotpressurized product gas can flow into the internal space 3025. As thecrankshaft 3034 rotates and the piston 3030 b descends within theexpander cylinder 3020, the hot pressurized product gas continues toflow into the internal space 3025, thereby maintaining a constantpressure within the internal space 3025 for the entire stroke.

In certain aspects of the operation, the inlet valve closes prior topiston 3030 b reaching the bottom of its travel. As the piston travelsfrom this intermediary point to bottom-dead-center, the gas pressurereduces and cools due to the expanding volumetric cavity.

The compressor cylinder 3010 and expander cylinder 3020 are coupled to acommon crankshaft 3034 and offset from each other by about 180 degreesof rotation of the crankshaft 3034, i.e. the piston 3030 b is at the topof its stroke when the piston 3030 a is at the bottom of its stroke. Asthe air-fuel mixture 3005 in the interior space 3015 of the compressorcylinder 3010 is initially, in this example, at atmospheric pressurewhile the pressure in the interior space 3025 is at or near the maximumpressure that will be reached at the end of the compression stroke inthe compressor cylinder 3010, there is a force imbalance for most of the180 degrees of rotation while the piston 3030 b is descending and thepiston 3030 a is ascending. It is this force imbalance that drives therotation of the crankshaft 3034. This force also drives the rotation ofgenerator 416, thereby creating power. In certain aspects, the generator416 generates electricity. In certain aspects, the generator 416generates pressurized fluid or produces mechanical work. As the piston3030 a of the compressor cylinder 3010 reaches the top of its stroke,there is a short period where the pressure in interior space 3015 isapproximately equal to the pressure in interior space 3025. While thereis no net driving force during this period, the inertia of the rotatingcrankshaft, which may include a flywheel (not shown in FIG. 3-1) toprovide increased rotational inertia, will carry the crankshaft past thetop-dead-center after which the compressor cylinder 3010 is drawing innew air-fuel mixture 3005 and the expander cylinder is exhausting thegas from the interior space 3025 through line 3080 and through therecuperator 3045 after which the gas is exhausted as exhaust 3085.

In certain aspects, the drive assembly 3036 is referred to as a splitcycle reciprocating engine having an intake that receives the air-fuelmixture 3005, the compressor cylinder 3010 is referred to as acompression chamber coupled to a reciprocating engine, and the internalspace 3015 is referred to as a reciprocating piston chamber. In certainaspects, the oxidizer 224 is referred to as an oxidation chamber that isconfigured to receive the mixture from the compression chamber via afirst inlet and to maintain oxidation of the mixture at an internaltemperature beneath a flameout temperature of the mixture and sufficientto oxidize the mixture without a catalyst. In certain aspects, theexpander cylinder 3020 is referred to as an expansion chamber thatreceives heated oxidation product gas from the oxidation chamber andexpands the product gas within the expansion chamber, thereby drivingthe reciprocating engine.

FIG. 3-2 is a conceptual depiction of the power generation system 3000of FIG. 3-1 according to certain aspects of the present disclosure. Theengine assembly 3036 is centrally mounted with the oxidizer 224 attachedat one end through the recuperator 3045 and heat exchanger 3055. In thisexample, LEC fuel, such as from a remote landfill 202 (not shown in FIG.3-2), is provided through line 3007 and the air-fuel mixture 3005 iscreated in the indicated box.

FIG. 3-3 is a schematic representation of another embodiment of aSchnepel cycle power generation system 3100 according to certain aspectsof the present disclosure. Many elements of system 3100 are common tosystem 3000 and their description is not repeated with respect to FIG.3-3. The system 3100 includes a turbine 3110 coupled to a compressor3105. The compressor 3105 functions in series with the reciprocatingpiston compressor 3010 such that the compression ratio of the pistoncompressor 3010 is reduced compared to system 3000 with the compressor3105 providing sufficient compression to bring the output from thepiston compressor 3010 up to the system pressure. In certain aspects,the system pressure of system 3100 is higher than the system pressure ofsystem 3000 thereby improving the efficiency. The output of thecompressor 3105 passes through the heat exchanger 3055 and into theoxidizer 224. The output of the oxidizer 224 passes through the turbine3110 before passing through the heat exchanger 3055 and then into thepiston expander 3020, after which the pressurized gas is exhausted tothe environment. The absolute pressures and temperatures of the fluid atvarious numbered points, shown in FIG. 3-3, in the system 3100 areprovided by way of illustration in the table below the drawing of FIG.3-3.

FIG. 3-4 is a schematic representation of another embodiment of aSchnepel cycle power generation system 3150 according to certain aspectsof the present disclosure. Many elements of system 3150 are common tosystem 3100 and their description is not repeated with respect to FIG.3-4. In this example, the air-fuel mixture 3005 is pressurized by thecompressor 3105 and then provided to the piston compressor 3010, whichis the reverse of the configuration of system 3100. The pressures andtemperatures of the fluid at various numbered points, shown in FIG. 3-4,in the system 3500 are provided in the table below the drawing of FIG.3-4.

FIG. 3-5 is a schematic representation of another embodiment of aSchnepel cycle power generation system 3200 according to certain aspectsof the present disclosure. Many elements of system 3200 are common topreviously presented systems and their description is not repeated withrespect to FIG. 3-5. In this embodiment, the output from the oxidizer224 is routed to the piston expander 3020 and then through the heatexchanger 3055 to the turbine 3110, after which the gas is exhausted.

FIG. 3-6 is a schematic representation of another embodiment of aSchnepel cycle power generation system 3250 according to certain aspectsof the present disclosure. Many elements of system 3250 are common topreviously presented systems and their description is not repeated withrespect to FIG. 3-6. In this embodiment, the air-fuel mixture 3005 iscompressed in the turbine-driven compressor 3105 ands then furthercompressed in the piston compressor 3010. The exhaust from the oxidizer224 passes through the heat exchanger 3055 then through the pistonexpander 3020 before passing through the turbine 3110 and beingexhausted.

FIG. 3-7 is a schematic representation of another embodiment of aSchnepel cycle power generation system 3300 according to certain aspectsof the present disclosure. Many elements of system 3300 are common topreviously presented systems and their description is not repeated withrespect to FIG. 3-7. This embodiment is similar to system 3250 exceptthat the output from the oxidizer 224 is provided to the piston expander3020 and then passes to the heat exchanger 3055.

FIG. 3-8 is a schematic representation of another embodiment of aSchnepel cycle power generation system 3350 according to certain aspectsof the present disclosure. Many elements of system 3350 are common topreviously presented systems and their description is not repeated withrespect to FIG. 3-8. This embodiment is similar to system 3250 exceptthat the output from the oxidizer 224 is provided to the heat exchanger3055 and then passes through the turbine 3110 before reaching the pistonexpander 3020, after which the gas is exhausted.

FIG. 3-9 is a schematic representation of another embodiment of aSchnepel cycle power generation system 3400 according to certain aspectsof the present disclosure. Many elements of system 3400 are common topreviously presented systems and their description is not repeated withrespect to FIG. 3-9. This embodiment is similar to system 3200 exceptthat the output from the oxidizer 224 is provided to the heat exchanger3055 and then passes through the turbine 3110 before reaching the pistonexpander 3020, after which the gas is exhausted.

FIG. 3-10 is a schematic representation of another embodiment of aSchnepel cycle power generation system 3450 according to certain aspectsof the present disclosure. Many elements of system 3450 are common topreviously presented systems and their description is not repeated withrespect to FIG. 3-10. This embodiment is similar to system 3200 exceptthat the output from the oxidizer 224 is provided to the heat exchanger3055 and then passes through the piston expander 3020 before reachingthe turbine 3110, after which the gas is exhausted.

Process Equipment Using Gradual Oxidation

FIG. 4-1 is a schematic of a three-stage gradual oxidizer fluid heatersystem 4000 according to certain aspects of the present disclosure. Apre-mixed air-fuel mixture 4005 is provided to a series of threeoxidizers 4010 a, 4010 b, and 4010 c. In certain aspects, the threeoxidizers 4010 a, 4010 b, and 4010 c are different in size andconfiguration. In certain aspects, the three oxidizers 4010 a, 4010 b,and 4010 c are substantially identical. The air-fuel mixture 4005 entersthe first oxidizer 4010 a where the fuel is consumed by a portion of theoxygen in the air and hot combustion products 4035 a are produced.Products 4035 a contain oxygen, as the proportion of fuel to oxidizerwas lean, i.e. excess air. The hot combustion products 4035 a aredirected through a first fluid heat exchanger 4020 a wherein heat istransferred from the hot combustion products 4035 a to the heat transferfluid, in this example water 430, which exits as a hotter fluid, in thisexample steam 4040. In certain aspects, a heat transfer fluid, such asan oil or a gas, is provided in place of the water 430 and the output ishot heat transfer fluid.

In certain aspects, the first oxidizer 4010 a is referred to as a firstreaction chamber that is configured to maintain gradual oxidation of thefirst fuel, i.e. the fuel component of the air-fuel mixture 4005, withinthe first reaction chamber without a catalyst while maintaining a firstinternal temperature within the first reaction chamber beneath aflameout temperature of the first fuel.

The product gases 4035 a then pass into a second oxidizer 4010 b andmixed with LEC fuel 4007. In certain aspects, the LEC fuel 4007 is mixedwith one of an oxidant, a diluent or flue gas, and a HEC fuel (none ofwhich are shown in FIG. 4-1) before being provided to oxidizer 4010 b.The fuel of the resultant mixture is consumed by a portion of the oxygenin the mixture and hot combustion products 4035 b are produced. The hotcombustion products 4035 b are directed into a second fluid heater 4020b wherein heat is transferred from the hot combustion products 4035 b toa separate flow of water 430 that exits as steam 4040 that is mixed withthe steam 4040 from the first heat exchanger 4020 a.

In certain aspects, the second oxidizer 4010 b is referred to as asecond reaction chamber that is configured to maintain gradual oxidationof the second fuel, i.e. the remaining fuel in the hot combustionproducts 4035 a and the newly introduced LEC fuel 4007, in a gradualoxidation process without a catalyst. In certain aspects, the secondoxidizer 4010 b comprises an oxygen sensor (not shown in FIG. 4-1) thatis coupled to a processor that is part of a controller (not shown inFIG. 4-1), wherein the processor is configured to determine an oxygencontent level.

The product gases 4035 b, or flue gas, then pass into a third oxidizer4010 c and mixed with additional LEC fuel 4007. In certain aspects, theLEC fuel 4007 to be provided to oxidizer 4010 c is mixed with one of anoxidant, a diluent or flue gas, and a HEC fuel (not shown in FIG. 4-1)before being provided to oxidizer 4010 c. In certain aspects, theair-fuel mixture provided to oxidizer 4010 c is different from theair-fuel mixture provided to oxidizer 4010 b. The fuel in the resultantmixture in oxidizer 4010 c is consumed by a portion of the oxygen in themixture and hot combustion products 4035 c are produced. These hotcombustion products 4035 c are directed into a third fluid heatexchanger 4020 c wherein heat is transferred from the hot combustionproducts 4035 c to a separate flow of water 430 that exits as steam 4040that is mixed with the steam 4040 from the first and second heatexchangers 4020 a and 4020 b.

The multiple stages of gradual oxidation, heat transfer to a fluid toreduce the gas temperature, and introduction of new fuel (FIG. 4-1) canbe used to limit the gas temperatures to below the thermal NOxtemperature threshold, while reducing the amount of oxygen exhaustingfrom the hot combustion products 4035 c. High efficiency, as measured bythe amount of energy transferred from the fuel 4005 and 4007 to thesteam 4040, provides that oxygen content leaving system 4000 via hotcombustion products 4035 c be as low as possible, typically 3-5% byvolume. It also provides that the exiting hot combustion products 4035 cbe as cool as possible. If one were to attempt to oxidize the fuel inone step, then the fuel-to-air ratio would be close to thestoichiometric value, which would yield high temperatures. For example,the adiabatic reaction temperature of methane at a stoichiometricapportionment is 3484° F., well above the threshold of 2300° F. for theformation of thermal NOx. The staged process of FIG. 4-1 cools thevarious gas flows 4035 a, 4035 b, 4035 c from the three oxidizers 4010a, 4010 b, and 4010 c so that more fuel can be introduced and oxidized,and the majority of oxygen can be removed from the system in the form ofH₂O and CO₂, without creating high temperatures and thermal NOx.

Other configurations of fluid flow from the input source, in thisexample water 430, to the output, in this example steam 4040, will beapparent to those of skill in the art. The system 4000 may have fewer orgreater numbers of oxidizers and heat exchangers. One or more heatexchanges 4020 a, 4020 b, etc. can be linked in series to increase thetemperature of the output fluid. The air-fuel mixture provided to eachoxidizer 4010 a, 4010 b, etc. can be different and adjustable inresponse to measurements of oxygen in the combustion products flow 4035a, 4035 b, etc.

A gradual oxidizer fluid heater arrangement 4000 facilitates theefficient oxidation of fuel and air in three stages and the capture ofthermal energy by a fluid. The first stage comprises a first gradualoxidizer which enables the gradual oxidation of a fuel and produces ahot, low-emission product gas stream that is directed into a first fluidheater where a first fluid stream is beneficially heated. In order toreduce or eliminate the likelihood of flashback and explosion of thefuel-air mixture 4005 entering the first-stage oxidizer 4010 a, theconcentration of fuel in the air-fuel mixture 4005 is limited to about20-90% of the lower flammability limit concentration of the fuel. Incertain aspects, it is desirable to limit the fuel content to 25-50%. Incertain aspects, there may be applicable fire safety standards thatlimit the allowable fuel concentration of the air-fuel mixture 4005.

After oxidation of the fuel in the first oxidizer 4010 a, the productgases 4035 a contain about 11-19% oxygen, plus carbon dioxide and watervapor, at a temperature of approximately 1500-2300° F. In certainaspects, the oxidation process is controlled such that temperature ofthe product gases 4035 a is 1600-2000° F. After transferring a portionof its heat to the heat transfer fluid in the heat exchanger 4020 a, theproduct gas 4035 a is at a temperature of 700-1300° F., and morepreferably 900-1200° F. At such a reduced temperature, a fuel stream4007 can be blended into the product gas 4035 a without undergoingimmediate reaction, which may occur at temperatures at or above 1400° F.The temperature of the mixed product gas 4035 a and fuel 4007 isnonetheless high enough to initiate oxidation reactions after anignition delay of 0.01 to 5 seconds. In certain aspects, the ignitiondelay is 0.1-0.5 seconds.

After the ignition delay has transpired, the mixture will have enteredthe second oxidizer 4010 b that is the preferred location for efficientoxidation of the fuel to occur. The second oxidizer 4010 b generates ahot product gas stream 4035 b with 2-16% oxygen at a temperaturepreferably between 1600-2000° F. that is directed into a second fluidheater 4020 b, where a portion of its thermal energy is transferred tothe heat transfer fluid. The temperature of product gas 4035 b is thenreduced to 900-1200° F. and a second stream of LEC fuel 4007 is blendedin product gas 4035 b without a premature reaction. The mixture of fuel4007 and product gas 4035 b enters a third oxidizer 4010 c, wherein theoxidation process repeats, producing an exhaust gas 4035 c with 1.5-14%oxygen. In certain aspects, between two and eight stages of gradualoxidation followed by fluid heating can be combined, with the ultimategoal of producing a final product gas stream with 1.5-5% oxygen and atemperature of approximately 150-700° F. In certain aspects, thetemperature of the final product gas stream is approximately 250-400° F.The heated fluid streams can be combined together, as shown in FIG. 4-1,or left apart.

FIG. 4-2 is a schematic of another embodiment of a three-stage gradualoxidizer fluid heater system 4100 according to certain aspects of thepresent disclosure. An air-fuel mixture 4005 enters a first oxidizer4110 a where the fuel is consumed by a portion of the oxygen in theair-fuel mixture 4005 producing heat which passes through a first steamcoil 4120 a and boils a stream of liquid water 4130 a to make saturatedsteam 4105. The cooled product gases 4035 a exit the first oxidizer 4110a and are mixed with additional LEC or HEC fuel and diluents 4007whereupon the mixture enters a second gradual oxidizer 4110 b. Similarto the reaction in the first oxidizer 4110 a, the fuel in thefuel-product gas mixture is consumed by a portion of the oxygen in themixture producing heat which passes through a second steam coil 4120 band boils a second stream of liquid water 4030 to make saturated steam4105. The cooled gases 4035 b exit the second oxidizer 4110 b and aremixed with additional fuel 4007 whereupon the mixture enters a thirdoxidizer 4110 c wherein the process repeats, heating the liquid water4130 in the third steam coil 4120 c to make saturated steam 4105.

It will be apparent to one of skill in the art that the fluid heatersystem 4100 may be used with a variety of heat transfer fluids. Forexample, an oil may be used to absorb heat from within one or more ofthe oxidizers 4110A, 4110 b, etc. Separate flows of different types ofheat exchange fluids may be individually provided to one or more of theoxidizers 4110 a, 4110 b, etc. and provided for separate use by externalsystems (not shown in FIG. 4-2). In certain aspects, one or more of theheat exchange coils 4120A, 4120B, etc. may be linked in series.

The partially-cooled product gases 4035 c are directed into aneconomizer 4140 wherein the available heat in the product gas 4035 craises the temperature of a subcooled liquid water stream 4150 to atemperature slightly less than the water's saturation temperature. Thecooled product gases 4035 d are exhausted to the atmosphere.

While similar to the more generic fluid heater of FIG. 4-1, onedistinguishing feature of system 4100 is the installation of a fluidheating element, i.e. a steam coil, into the same unit as the gradualoxidizer. The preferred temperature ranges and oxygen levels at the exitof each stage are the same as in the prior embodiment. A final heatrecovery unit, i.e. economizer 4140, is added to the tail end of theproduct gas stream to extract as much heat as possible from the gasesbefore they exhausted to atmosphere. The steam coils 4120 a, 4120 b,4120 c may be embedded in the porous ceramic bed of the oxidizers 4110a, 4110 b, 4110 c or suspended above the top of the bed. In certainaspects, additional bed height or a porous, partial radiation shield maybe added between the gradual oxidation zone and the steam generationzone to help ensure the gases aren't quenched by the relatively coldsurfaces of the steam coils 4120 a, 4120 b, 4120 c before the gradualoxidation reactions are complete.

FIG. 4-3 is a schematic representation of a single-stage recuperativesteam generation system 4200 according to certain aspects of the presentdisclosure. Air 4210 is directed into the cold side of a recuperator3045 where it receives heat and exits as a preheated air stream that iscombined with a reduced-oxygen, recirculated product gas stream 4225 towhich is added an LEC fuel 4220. In certain aspects, the LEC fuel 4220comprises a HEC fuel. In certain aspects, LEC or HEC fuel can be mixedwith the air 4210 prior to entering the recuperator 3045.

The air-fuel-diluent mixture enters an oxidizer 224 where the fuel isconsumed by a portion of the oxygen and produced heat.

A liquid water stream 4230 is heated in the economizer 3055 to create ahot water stream that is directed to the steam coil 4240. A portion ofthe heat from the oxidation process is transferred through the steamcoil 4240 into the hot water, thereby creating steam 4242 for beneficialuse. The partially-cooled product gases exit the oxidizer 224 and aredivided into two streams. A portion of the product gases is directedthrough a recirculation blower 4245 where the product gases exit at aslightly higher pressure and are combined with the air-fuel stream asdescribed above. The remaining portion of the product gases passesthrough the economizer 3055 where more heat is removed, thereby heatingthe incoming water 4230, and the cooled product gases then pass throughthe hot side of the recuperator 3045 where additional heat is removed,thereby heating the incoming air 4210, before the fully-cooled productgases exit to atmosphere.

System 4200 inhibits flashback and explosion of the pre-mixed air-fuelmixture by maintaining the oxygen concentration of the mixture enteringthe oxidizer 224 at less than 12%, and preferably less than 9%, throughthe recirculation of the product gases 4225. The recirculation providesfor oxidizer inlet temperatures in the range of 700-1300° F., andpreferably 900-1200° F. Through recirculation, this embodiment alsogenerates a total hot gas flow rate through the oxidizer equal to1.5-4.0 times, preferably 2.0-3.0 times, the exhaust flow. The greaterhot gas flow rate permits the installation of more heat transfer surfacearea within the oxidizer 224 and the production of greater amounts ofsteam. The specific heat (c_(p)) of the gas stream performing the heattransfer to the steam coils is also greater than the specific heat ofoxidation products that have less CO₂, less H₂O, and more O₂. Greaterspecific heat leads to greater potential for heat transfer, with a fixedtemperature difference between the cold and hot streams.

System 4200 incorporates an economizer 3055 that recovers heat from theproduct gas stream by raising the temperature of the water 4230 to justbelow its boiling point. System 4200 also incorporates a recuperator3045 that recovers additional heat by preheating the combustion airbefore it enters the oxidizer 224. This recuperator 3045 reduces oreliminates the amount of auxiliary heating that is added to initiate thegradual oxidation process within the oxidizer 224 and also reduces theloss of heat in the exhaust.

FIG. 4-4 is a schematic representation of a two-stage water-tube type ofsteam generation system 4300 according to certain aspects of the presentdisclosure. An air-fuel mixture 4005 is provided at a bottom inlet of anoxidizer 4321. The air-fuel mixture 4005 flows through the sparger tree4322 and enters the porous media 512 where gradual oxidation occurs andall the fuel is consumed by a portion of the oxygen. A portion 4315 ofthe hot product flue gas exits the bed 512 and passes through steamcoils 4325 where heat is removed from the gas, while a smaller portion4314 of the hot gas passes through a core zone where no steam coils arelocated and no heat is removed. The first steam coils 4325 are arrangedaround the circumference of the enclosure, so that product gases 4314flowing upward in the vicinity of the center axis of the enclosure willremain at a high temperature and serve as an ignition source for the2^(nd) stage gradual oxidation occurring just in the upper section.

Additional LEC fuel or HEC fuel with diluents 4220 is injected into themiddle zone of the oxidizer 4321 and mixes with the product gases 4315to form an oxidant-diluent-fuel mixture 4316 that enters an invertedsparger cone 4324 through a plurality of horizontal spokes thatpenetrate through the walls of the cone 4324. These spokes have aplurality of injection holes to distribute mixture 4316 in a nearlyuniform manner. The hot gas portion 4314 enters the inverted spargercone 4324 through an opening at the bottom and serves to initiategradual oxidation of the mixture streams 4316 thereby consuming theadditional fuel and generating a reduced-oxygen, hot product stream4317.

The product stream 4317 is directed through steam coils 4326 where heatis removed from the product stream 4317 that then exits the oxidizer4321 as cooled product gases 4318. Water 4353 at near-saturatedconditions is admitted into each of the steam coils 4325 and 4326 andexits as saturated steam streams 4354. A two-stage, water-tube-style,gradual oxidizer steam generator 4300 is arranged in a single enclosure,and equipped with a means for reducing gas pressure drop in the secondstage. A vertical enclosure incorporates a first gradual oxidizer foroxidizing fuel and creating a hot product gas stream, followed by afirst set of steam coils (water tubes) to remove heat from the productstream.

The quantity of water or steam directed to the final coils 4326 may begreater than the prior stages to remove as much heat as possible fromthe gas flow 4317 before it exits to the atmosphere as exhaust 4318.While it is desirable to maintain product gas temperature above 900° F.as it exits primary or intermediate stages (4316), dropping below 900°F. is not a concern in the very last stage of a multistage systembecause there is no subsequent gradual oxidizer that requirestemperatures above 900° F. The steam generation surface area and or anyeconomizer surface area can be as large as desired to achieve theobjective of heat removal in the final stage.

FIG. 4-5 is a schematic representation of a two-stage fire-tube type ofsteam generation system 4400 according to certain aspects of the presentdisclosure. An air-fuel mixture 4005 enters the bottom zone of a spargertree 4422. The air-fuel mixture 4005 flows through the sparger tree 4422and enters the bed of porous ceramic 512 where gradual oxidation occursand all the fuel is consumed by a portion of the oxygen. The hot productgas 4419 exits the porous media 512 and enters fire tubes 4425 whereheat is removed from the gas by the surrounding water 4451.

Additional LEC or HEC fuel 4220 and optionally diluents (not shown) aremixed with the cooled product stream 4419 to form anoxidant-diluent-fuel mixture, which is admitted into the second sparger4426 and the second bed of porous media 512 wherein the additional fuelis consumed and a reduced-oxygen, hot product stream 4415 is generatedand directed through fire tubes 4429 where heat is removed by thesurrounding water 4451. The cooled product gases 4415 collect in aplenum 4430 and exit the oxidizer as a cooled exhaust stream 4417. Thetwo gradual oxidation zones have insulated walls 4424, 4428 to preventexcessive cooling of the reactant gases which leads to undesiredquenching of the gradual oxidation reactions. Water 4451 at subcooled ornear-saturated conditions is admitted into the gradual oxidizerenclosure 4401 and exits as saturated steam 4452. In certain aspects,additional heating surfaces are added for superheating the steam 4452 toa temperature substantially higher than its boiling point. In certainaspects, the water 4451 is pressurized leading to higher saturated steamtemperatures.

By reducing the oxygen in the final exhaust gas stream to 1.5-5.0% whilereducing the exit gas temperature to 250-400° F., the overall cycleefficiency is estimated to be 85-90%, which represents an improvementover conventional steam generators that operate at 80-86% cycleefficiency. Increased cycle efficiency corresponds to reduced fuel usagefor the same useful heat output.

By maintaining gradual oxidation temperatures below about 2300° F., andpreferably below 2000° F., the formation of thermal NOx is reduced.Conventional burners have flames with maximum reaction temperaturesexceeding 2300° F. and generate substantially more NOx than a gradualoxidation process.

In certain aspects, electric heating elements (not shown in FIG. 4-5)are located at the inlet of one or both of the oxidizer stages to helpinitiate oxidation of the air-fuel mixture 4005 or oxidant-diluent-fuelmixture at that location.

In certain aspects, porous ceramic media 512 is reduced in amount or notpresent and the reaction temperature is allowed to go higher in the openvolume. Furthermore, if the porous media is removed, a greater fractionof the total flow can be distributed to the final sparger 4426.

In certain aspects, the internal pressure is maintained low enough sofuel can be added at each stage using only line pressure, i.e. without agas pressure booster.

In certain aspects, an economizer or recuperator (not shown in FIG. 4-4or 4-5) is added to condense the moisture of combustion from the productgases, or alternatively to leave the water in the vapor phase.

In certain aspects, a fluidized bed (not shown in FIG. 4-4 or 4-5)similar to the system shown in FIG. 1-13 replaces the porous media 512to facilitate heat feedback and ignition in the oxidizer 4321, 4401 aswell as enhance heat transfer to the steam coils. Other options includeflue-gas recirculation and structured media, similar to the systemsshown in FIGS. 1-15 and 1-16A/16B.

FIG. 4-6 schematically depicts the flow through a gradual oxidationsystem 4600 having a sparger according to certain aspects of the presentdisclosure. The processes and elements of FIG. 4-6 are described inrelation to the system 4500 of FIG. 1-12, wherein steps 1-6 areaccomplished, which is shown as receiving the output from point A ofsystem 4500. In certain aspects, air 4602 and fuel 4220 are mixed, forexample using a mixer similar to mixer 4510 of system 4500, and providedin place of point A in FIG. 4-6. The gas mixture entering from point Aundergo the following process steps:

-   -   7. The hot gas leaving the lower section is split into portions        4315 and 4314, wherein portion 4315 is passed through a heat        exchanger, such as the coils 4325 of FIG. 4-4, and a portion of        the heat extracted from the hot gas, thereby cooling the gas to        temperatures proximate to the autoignition temperature. This        stage uses the heat extracted to generate steam or vaporize        another liquid.    -   8. In this example, fuel 4220 is injected into both streams 4314        and 4315. The 4314 portion is hot enough to initiate gradual        oxidation in the portions that are mixed in each stage 4630.

Hybrid Cycles and Gradual Oxidation

FIG. 5-1 is a schematic diagram of an exemplary gradual oxidation system5100 incorporating steam generation and additional fuel injectionaccording to certain aspects of the present disclosure. A compressor 410is coupled to a shaft that is further coupled to a turbine 414 and apower generator 416, as previously shown in FIG. 1-9. An air-fuelmixture 5102 is provided to a compressor 410 that provides a pressurizedair-fuel mixture 206 f to a heat exchanger 418 that heats this mixture206 f with heat from the turbine exhaust 420. The hot, pressurizedmixture 206 g is conveyed into the oxidizer 224. In certain aspects, anadditional air-fuel mixture 5104, is injected into the oxidizer. Incertain aspects, the air-fuel mixture 5104 comprises only LEC or HECfuel. The air-fuel mixtures 206 g and 5104 are gradually oxidized in theoxidizer 224 and the hot flue gas 226 is exhausted to the turbine 414.In passing through the turbine, energy is extracted from the hot fluegas 226 and the cooled, expanded turbine exhaust 420 is passed back tothe heat exchanger 418. After passing through the heat exchanger 418,the flue gas 420 may still comprise free oxygen. Additional air-fuelmixture 5112 is injected into the flue gas 420 within a duct burner 5110to reheat the flue gas to produce a hot flue gas 5111, which then passesthrough a heat exchanger 422 wherein heat is transferred from the hotflue gas 5111 to water 430 thereby producing steam 5108 which isprovided to an end use (not shown in FIG. 5-1). The cooled flue gas isnow exhausted as exhaust stream 5106 to the environment. In certainaspects, the air-fuel mixture 5102 comprises only air and fuel isprovided from air-fuel mixture 5104.

FIG. 5-2 is a schematic diagram of an exemplary gradual oxidation system5200 incorporating steam generation and cogeneration according tocertain aspects of the present disclosure. Many elements of system 5200are common to the system 5100 previously discussed and their descriptionis not repeated with respect to FIG. 5-2. In system 5200,steam-generating coils 5220 are embedded in the oxidizer 224. Extractionof heat from the oxidation process within the oxidizer 224 reduces themaximum reaction temperature, thereby reducing NOx formation, whilegenerating steam 5204. The air-fuel mixture 5104 is then injected intothe cooled gas within the oxidizer 224 that is “downstream” of the coils5220, thereby allowing additional combustion so as to reduce the oxygenlevel in the exhaust 226 going into the turbine 414. This injection ofadditional fuel and the further combustion that reduces the oxygenwithin the exhaust 226 increases the mass flow through the turbine 414,increases the specific heat of exhaust gas 226, and decreases the ratioof specific heats, thereby increasing the power output of the turbine414. System 5200 eliminates the duct burner 5110 while still producingsteam from the coils 5220. As the coils 5220 operate at the peaktemperature of the system 5200, the steam 5204 will be at a highertemperature or pressure than the steam 5108 produced in system 5100.

In certain aspects, steam 5230 is injected into the working fluid withinoxidizer 224. Injection of steam in the gradual oxidation process withinoxidizer 224 could help reduce emissions while burningnear-stoichiometric air-fuel ratios. In certain aspects, injection ofsteam 5230 allows pre-mixed air-fuel mixtures 206 g to be closer to astoichiometric ratio without exceeding the flammable range of theair-fuel mixture 206 g due to the inert water vapor present. In certainaspects, the steam is injected in a manner to create a swirling flowpattern within the oxidizer 224, further aiding in the gradual oxidationprocess. In certain aspects, the steam 5230 is introduced through axialpipes (not shown in FIG. 5-2) having radial holes and positioned aroundthe perimeter of the oxidizer 224. In certain aspects, steam 5204 fromthe coils 5220 is returned as steam 5230 and, if the steam 5204 is at apressure equal to or greater than the pressure within oxidizer 224,there is less parasitic energy loss because the steam 5230 is alreadypressurized.

FIG. 5-3 is a schematic diagram of an exemplary gradual oxidation system5300 incorporating dual compressors 410, 5308 with intercoolingaccording to certain aspects of the present disclosure. Many elements ofsystem 5300 are common to the systems 5100 and 5200 previously discussedand their description is not repeated with respect to FIG. 5-3. The useof intercooler 5304 allows a higher total compression across compressors410 and 5308, thereby improving the efficiency of the system 5300.Intercooler 5304 cools stream 5302 which is further compressed by 5308.A lower temperature into compressor 5308 reduces the amount ofthermodynamic work, i.e., power, used to compress the gas. Theintercooler permits the flow at 5310 to be at a lower temperature thanwould exist without intercooler 5304. This permits more thermal energyto be recovered in recuperator 418. The amount of recovered energy inrecuperator 418 is proportional to the temperature difference betweenthe turbine exhaust 420 and the recuperator inlet temperature 5310.

FIG. 5-4 is a schematic diagram of an exemplary gradual oxidation systemincorporating a starter gradual oxidizer according to certain aspects ofthe present disclosure. Many elements of system 5400 are common to thesystems 5100, 5200, and 5300 previously discussed and their descriptionis not repeated with respect to FIG. 5-4. The air-fuel mixture 5102 isprovided as a flow of warmed, compressed air-fuel mixture 5408 to aninlet of oxidizer 224. Use of a starter oxidizer 5420 allows the mainoxidizer 224 to be brought up to operating temperature, i.e. above theautoignition temperature of the warmed, compressed air-fuel mixture5408, with a reduced amount of NOx formation compared to using aconventional combustor burning a HEC fuel in an open flame (for example,FIG. 1-10). The starter oxidizer 5420 is provided with a supply of anair-fuel mixture 5428 and, in certain embodiments, pressurized with ablower 5422. The hot combustion product gases, i.e. flue gas, isprovided from an outlet of the starter oxidizer 5420 to an inlet on theoxidizer 224. In certain embodiments, the flue gas from the starteroxidizer 5420 enters the oxidizer 224 through the same inlet as thewarmed, compressed air-fuel mixture 5408. A valve 5426 is provided toshut off this start-up subsystem when the main oxidizer 224 reachesoperational temperature and the compressor/turbine 410/414 subsystem isstarted. In system 5400, filters 5402 and 5424 are provided to removeparticulates and other undesired components from the respective air-fuelmixtures 5102 and 5428.

The advantages of using a starter gradual oxidizer of FIG. 5-4 includereduction of emissions of criteria pollutants, for example NOx, duringstart-up of the system. It also allows the use of the native LEC gas atthe site, rather than retaining a separate HEC supply of fuel forstart-up combustion systems.

FIG. 5-5 is a schematic diagram of an exemplary gradual oxidation system5500 incorporating multiple points 5504, 5510, 5516, and 5522 of water430 injection according to certain aspects of the present disclosure.Many elements of system 5500 are common to the systems 5100-5400previously discussed and their description is not repeated with respectto FIG. 5-1 through FIG. 5-4. Processes subsequent to each injectionpoint 5504, 5510, 5516, and 5522 will vaporize some amount of water inthe process input to a gas while cooling the process output gas flow dueto the latent heat of evaporation of the injected water. Water injectionmay be strategically performed at individual locations only, or incombination with other water injection locations.

Water injection at location 5504 can be used to cool the inlet flowstream temperature of compressor 410. Lower inlet temperatures increasethe density of the fluid entering the gas turbine cycle, increasing thepower output. Cooler compressor inlet temperatures also reduce theamount of work (power) used to compress gas 5508, leaving more shaftpower 412 available to drive generator 416.

Water injection at locations 5510, 5516, and into heat exchanger 418increase the power output of the turbine cycle. Compression of liquidwater, as typically performed by a pump, can be more efficient thancompressing a gaseous mixture in compressor 410. Turbine 414 willgenerate more work due to the higher amount of mass flow of flue gas.These cycles are sometimes referred to as “humid air cycles” in the art.System 5500 can therefore leverage the beneficial effects of waterinjection in a cycle, while not producing thermal NOx due to the gradualoxidizer process.

Injection and evaporation of water in recuperator 418 can present morethan just the thermodynamic cycle performance advantages listed in theprior paragraph. Recuperator 418 is naturally being heated by theexhaust flow 5526. Evaporation of water can increase the effective heattransfer coefficient of the flow between 5512 and 5514, thereby enablinga smaller physical heat exchanger.

Other embodiments and methods of injecting water can also be used inaccordance with the description provided herein. For example, othersystems and methods of injecting water into the oxidation system aredescribed in U.S. application Ser. No. 13/048,796, filed Mar. 15, 2011,the entirety of which is incorporated by reference herein to the extentthe teachings of that application are not inconsistent with the presentdescription.

FIG. 5-6 is a diagram 5600 of the gas content of the exhaust of varioussystems. It can be seen that conventional gas turbines generally operatewith greater than approximately 9%, by mass, residual free oxygen in theexhaust stream. By using the gradual oxidation techniques in theoxidizer of FIG. 5-2 and FIG. 5-3 while generating simultaneous steam,the oxygen content exiting the oxidizers and gas turbine cycles will belower, preferably in the 1.5-5% range. FIG. 5-6 shows this to be wellbelow the range for conventional gas turbines. Hence, the simultaneousgeneration of pollutant-free flue gas and steam in a gradualoxidizer/steam generator, for example system 5200 of FIG. 5-2, is novelin the art. And as discussed previously in this document, lower oxygenand higher levels of CO₂ and H₂O are beneficial to the Brayton gasturbine cycle.

Control of the gradual oxidation system can be performed in a number ofways. In certain aspects, a method of ensuring complete oxidationchanges the residence time of the fuel and air mixture within theoxidizer vessel. In certain aspects, a gas turbine supplies the gradualoxidizer and the turbine is configured to vary its rotational speedusing, for example, variable speed generators and power electronics orinverters, as are known to those of skill in the art. In certainaspects, a fan feeds a fuel and air mixture to an oxidizer, for exampleas shown in FIG. 2-1, and the fan is powered by a variable speed drive,with the fan speed reduced to increase residence time inside theoxidizer.

In some embodiments, the oxidation systems described herein can be usedfor oxidizing fuel in a flexible, efficient, and clean manner. Theoxidation reactions described herein provides methods for the oxidationof waste materials and the prevention or minimization of air pollutionthereby. For example, methods and systems of how the oxidation reactionscan be used are provided in U.S. patent application Ser. Nos.13/115,910, filed May 25, 2011, and 13/115,902, filed May 25, 2011, bothof which are incorporated herein by reference in their entirety to theextent their teachings are not inconsistent with the descriptionsprovided herein.

The previous description is provided to enable a person of ordinaryskill in the art to practice the various aspects described herein. Whilethe foregoing has described what are considered to be the best modeand/or other examples, it is understood that various modifications tothese aspects will be readily apparent to those skilled in the art, andthe generic principles defined herein may be applied to other aspects.Additionally, although various embodiments are described in differentsections, paragraphs, and with respect to different figures, unlessotherwise expressed, various embodiments may be combined with otherdescribed embodiments. Thus, the claims are not intended to be limitedto the aspects shown herein, but is to be accorded the full scopeconsistent with the language claims, wherein reference to an element inthe singular is not intended to mean “one and only one” unlessspecifically so stated, but rather “one or more.” Unless specificallystated otherwise, the terms “a set” and “some” refer to one or more.Headings and subheadings, if any, are used for convenience only and donot limit the disclosure.

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an illustration of exemplary approaches. Basedupon design preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged. Some of the stepsmay be performed simultaneously. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

Terms such as “top,” “bottom,” “front,” “rear” and the like as used inthis disclosure should be understood as referring to an arbitrary frameof reference, rather than to the ordinary gravitational frame ofreference. Thus, a top surface, a bottom surface, a front surface, and arear surface may extend upwardly, downwardly, diagonally, orhorizontally in a gravitational frame of reference.

A phrase such as an “aspect” does not imply that such aspect isessential to the subject technology or that such aspect applies to allconfigurations of the subject technology. A disclosure relating to anaspect may apply to all configurations, or one or more configurations. Aphrase such as an aspect may refer to one or more aspects and viceversa. A phrase such as an “embodiment” does not imply that suchembodiment is essential to the subject technology or that suchembodiment applies to all configurations of the subject technology. Adisclosure relating to an embodiment may apply to all embodiments, orone or more embodiments. A phrase such an embodiment may refer to one ormore embodiments and vice versa.

The word “exemplary” is used herein to mean “serving as an example orillustration.” Any aspect or design described herein as “exemplary” isnot necessarily to be construed as preferred or advantageous over otheraspects or designs.

As used herein, listings that recite “at least one of A, B, and C” or“at least one of A, B, or C” are intended to mean only A, only B, onlyC, or any combination of A, B, and C, including all of A, B, and C.

All structural and functional equivalents to the elements of the variousaspects described throughout this disclosure that are known or latercome to be known to those of ordinary skill in the art are expresslyincorporated herein by reference and are intended to be encompassed bythe claims. Moreover, nothing disclosed herein is intended to bededicated to the public regardless of whether such disclosure isexplicitly recited in the claims. No claim element is to be construedunder the provisions of 35 U.S.C. §112, sixth paragraph, unless theelement is expressly recited using the phrase “means for” or, in thecase of a method claim, the element is recited using the phrase “stepfor.” Furthermore, to the extent that the term “include,” “have,” or thelike is used in the description or the claims, such term is intended tobe inclusive in a manner similar to the term “comprise” as “comprise” isinterpreted when employed as a transitional word in a claim.

What is claimed is:
 1. A method for oxidizing fuel, comprising:receiving a gas comprising an oxidizable fuel into an oxidizer having areaction chamber with an inlet and an outlet, the reaction chamberconfigured to maintain an oxidation process of the gas; and changing atleast one of (i) removal of heat from the reaction chamber and (ii) aninlet temperature of the reaction chamber when at least one of (a) anactual temperature within the reaction chamber approaches or increasesto a flameout temperature of the fuel and (b) the reaction chamber inlettemperature approaches or drops below an autoignition threshold of thefuel.
 2. The method of claim 1, wherein the actual temperature of thereaction chamber is maintained below the flameout temperature.
 3. Themethod of claim 1, wherein the inlet temperature of the reaction chamberis increased to a level that will support oxidation of the fuel withouta catalyst.
 4. The method of claim 1, wherein the inlet temperature isincreased to above the autoignition threshold.
 5. The method of claim 1,wherein a temperature of the gas is increased by a heat exchangerlocated within the reaction chamber.
 6. The method of claim 1, furthercomprising expanding gas from the reaction chamber outlet in a turbineor a piston engine.
 7. The method of claim 1, further comprisingcompressing the fuel with a compressor prior to introduction of the fuelmixture into the reaction chamber.
 8. The method of claim 1, whereinremoval of heat from the reaction chamber comprises introducing a liquidinto the reaction chamber.
 9. The method of claim 8, further comprisingevacuating the liquid from the reaction chamber.
 10. The method of claim9, wherein the liquid is evacuated from the reaction chamber in the formof steam.
 11. The method of claim 1, wherein the reaction chambermaintains gradual oxidation of the oxidizable fuel without a catalyst.12. The method of claim 1, wherein heat is removed from the reactionchamber when the temperature within the reaction chamber exceeds 2300°F.
 13. The method of claim 1, wherein the oxidizable fuel comprises atleast one of hydrogen, methane, ethane, ethylene, natural gas, propane,propylene, propadiene, n-butane, iso-butane, butylene-1, butadiene,iso-pentane, n-pentane, acetylene, hexane, and carbon monoxide.
 14. Amethod for oxidizing fuel, comprising: receiving a gas comprising anoxidizable fuel into an oxidizer having a reaction chamber with an inletand an outlet, the reaction chamber configured to maintain a gradualoxidation process; and increasing at least one of (i) removal of heatfrom the reaction chamber when an adiabatic reaction temperature withinthe reaction chamber approaches a flameout temperature of the fuel; and(ii) an inlet temperature of the reaction chamber when the reactionchamber inlet temperature drops below an autoignition threshold of thefuel.
 15. The method of claim 14, wherein an actual temperature of thereaction chamber is maintained below the flameout temperature.
 16. Themethod of claim 14, wherein the inlet temperature of the reactionchamber rises to a level that will support oxidation of the fuel withouta catalyst.
 17. The method of claim 14, wherein the inlet temperaturerises above the autoignition temperature.
 18. The method of claim 14,wherein a gas temperature is increased by a heat exchanger locatedoutside the reaction chamber, and the gas is passed through the heatexchanger prior to being introduced into the reaction chamber.
 19. Amethod for oxidizing fuel, comprising: receiving a gas comprising anoxidizable fuel into an oxidizer having a reaction chamber with an inletand an outlet, the reaction chamber configured to maintain a gradualoxidation process without a catalyst; and increasing at least one of (i)removal of heat from the reaction chamber when a reaction temperaturewithin the reaction chamber approaches a flameout temperature of thefuel, such that an actual temperature of the reaction chamber ismaintained below the flameout temperature; and (ii) an inlet temperatureof the reaction chamber when the reaction chamber inlet temperaturedrops below an autoignition threshold of the fuel, such that the inlettemperature of the reaction chamber is maintained above a level thatwill support oxidation of the fuel without a catalyst.
 20. The method ofclaim 19, wherein the inlet temperature is maintained above theautoignition temperature.